Locke: knowledge and its limitsIan TiptonIThat John Locke’sEssay concerning Human Understandingis one of the philosophicalclassics is something nobody would deny, yet it is not easy to pinpoint precisely what isso special about it. Locke himself has been described as the founder of Britishempiricism, but labels of this sort are increasingly treated with suspicion, and someaffinities to Descartes, usually regarded as the first of the great rationalist philosophers,have also been widely acknowledged. Students studying his philosophy will spend sometime pondering on his advocacy of a distinction between primary and secondary qualities,but they will also be told that the doctrine had a long history and that, in Locke’s ownday, it was central to the theorizing of Robert Boyle and the ‘new science’ generally.They may dwell too on his talk of a materialsubstratumof qualities, but they may also betold that his thinking here was confused, and that at this point anyway he was stronglyinfluenced by the scholastic philosophy he saw himself as trying to break away from.They are likely to be puzzled by his talk of ‘ideas’ as the Objects’ of thought—he tells usat one point that ‘the Mind…perceives nothing but its ownIdeas’ (IV.iv.3)1—if onlybecause, on the face of it, this poses the obvious problem that, as Berkeley was to stress,it seems to rule out the possibility of the very knowledge of the ‘real’ world that Lockeclearly took it for granted we have. Locke himself confesses that theEssayis too long—‘the way it has been writ in, by catches, and many long intervals of Interruption, beingapt to cause some Repetitions’ (Epistle to the Reader)—and his style makes it neithereasy nor attractive to read; yet it richly rewards study. That this would be agreed both bythose who have thought him guilty of fundamental errors throughout and by those whosee him as belonging most decidedly to our age, and as characteristically judicious andsane, merely adds to the fascination of his work and encourages deeper study.Thisfascination is increased when we realize that in his own time he was often considered adangerous and subversive thinker.Locke was born at Wrington, Somerset, in 1632. He attended Westminster School andChrist Church, Oxford, where he retained his Studentship until 1684. After anintroduction to the world of diplomacy when he was involved in a mission toBrandenburg he set out to qualify in medicine, working at one stage with ThomasSydenham, the great physician whom, in the Epistle to the Reader which prefaces theEssay,he describes, along with Robert Boyle, Christiaan Huygens, the Dutch astronomerand physicist, and ‘the incomparable Mr. Newton’, as one of the ‘Master-Builders, whosemighty Designs, in advancing the Sciences, will leave lasting Monuments to theAdmiration of Posterity’. Locke had worked with Boyle too, and Boyle was clearly oneimportant influence on theEssay,just as Lord Ashley, afterwards Earl of Shaftesbury, towhom he became personal physician in 1667 and also a political adviser, influenced hispersonal fortunes. Locke was to serve Shaftesbury in various capacities, becoming,eventually, Secretary to the Council of Trade and Plantations, of which Shaftesbury wasPresident. This body was dissolved in 1675. In the same year Locke’s deteriorating healthled to him departing for France. He stayed first in Montpellier, but in Paris was able tomake new contacts, including François Bernier, a leading disciple of Gassendi, aphilosopher who had almost certainly influenced the development of his thinking, evenbefore this period.2 Locke returned to England, and to an increasingly troubled politicalscene, in 1679. Before long Shaftesbury was forced to flee to Holland, where he died in1683, and later that year Locke himself left for Holland, returning only after James II hadbeen deposed and William of Orange had secured the English throne. Locke’sEssaywaspublished not long after, in 1690, and it was regarded at once as both important andcontroversial. However, apart from engaging in a time-consuming controversy withEdward Stillingfleet, Bishop of Worcester, Locke showed little inclination to getinvolved in arguments with his critics, not even Leibniz, who attempted repeatedly toengage in correspondence with him, though hisNew Essays on Human Understandingwas not published until long after the death of both men. Locke published other worksafter his return from Holland, including theTwo Treatises of Government,discussed inthe next chapter, but his health continued to fail. He was to spend the last years of his lifein the house of Sir Francis Masham and his wife Damaris, daughter of the CambridgePlatonist Ralph Cudworth, and herself a woman of impressive intellect with whomLocke, a lifelong bachelor, had, it seems, once been in love. He died in 1704.Even this brief sketch of Locke’s life will be sufficient to show that it was an eventfulone, and each stage had its impact on the development of Locke’s intellectual life. He didnot publish anything of importance until he was in his fifties, but hisSome Thoughtsconcerning Education(1693) reflects his critical attitude to the sort of education he hadhimself encountered at Westminster School. His dissatisfaction with the sort ofphilosophy taught at Oxford when he was there, which he described as ‘perplexed withobscure terms and useless questions’, influenced the development of theEssay,as, morepositively, did his reading of Descartes who, he was to tell Stillingfleet, offered him ‘myfirst deliverance from the unintelligible way of talking’ of the schools. His associationwith Shaftesbury involved him in practical affairs, and it is no surprise that hispublications should includeSome Considerations of the Consequences of the Lowering ofInterest, and Raising the Value of Money(1692), as well asA Letter concerningToleration(1689), which championed religious toleration, of which Shaftesbury had beena proponent. The likely influence of Gassendi, which probably antedated Locke’sacquaintance with Bernier, has already been mentioned, and R. I. Aaron is onecommentator who has stressed the influence of the Cambridge Platonists, claiming that‘Much of the fourth book of theEssaymight have been written by one of the CambridgeSchool’.3 One could go on, even in a way that might suggest that Locke was hardly anoriginal thinker at all, though that would be grossly unfair. A fairer estimate would be tosee him as a child of his time, certainly, but as making a major contribution to the debatesand disputes which characterized the period in a way which led to a recognition of hisimportance at the time, though not always for the reasons that have been most widelystressed since. In very general terms, he can be seen as a spokesman for his age who alsohelped mould that age. In addition, he was to come to be seen, somewhat distortedly, asthe originator of a school, the British empiricists, diametrically opposed to the rationalismstemming from the philosophy of Descartes. From either point of view hisEssayconcerning Human Understandingwill be seen as an important legacy, and to that wenow turn.IIThere are two well-known passages in the Epistle to the Reader which help focus ourminds on the aims and purposes of theEssay,one being that in which Locke praises the‘Master-Builders’, scientists such as Boyle, with respect to whom he contrasts himself as‘an UnderLabourer…clearing Ground a little, and removing some of the Rubbish, thatlies in the way to Knowledge’. This passage makes his project look modest, but it alsosuggests that, in so far as he sees himself as having opponents, these are not so much theCartesians as the Aristotelians, or those proponents of the debased scholasticism whichfor many still constituted learning, but which was characterized by the ‘frivolous use ofuncouth, affected, or unintelligible Terms’ which Locke goes on to complain of. There ismuch in theEssaythat could be described as rubbish-removal, from the attack on innateprinciples in Book 1, to, for example, criticism of the doctrine of substantial forms.However, this passage does suggest that Locke’s project is negative, so it must be addedboth that, in practice, rubbish-removal usually goes along with positive alternativedoctrines, and that in the other passage in the Epistle he gives a rather different accountof his aims. Here he tells us how theEssaycame to be written, referring to a meeting withfriends—usually thought to have taken place in the winter of 1670–I—when an issueVery remote’ from that discussed in theEssaywas being debated and they ‘foundthemselves quickly at a stand, by the Difficulties that rose on every side’. Locke’sresponse, he tells us, was to consider whether the question that perplexed them was onethey could hope to resolve. More generally, he suggested, ‘it was necessary to examineour own Abilities, and see, what Objects our Understandings were, or were not fitted todeal with’. This topic set the agenda for theEssay. Locke could indeed have given hiswork the title ‘Human Knowledge: Its Scope and Limits’, which was the title which, overtwo hundred years later, Bertrand Russell gave to one of his books.Even this, however, can make Locke’s project look very negative, but what he goes onto stress in the first chapter of Book I is the positive advantages of this approach whichare, first, that an enquiry into the limits of the understanding will enable us to concentrateour minds upon matters we can tackle with some hope of success, and second, and as aconsequence, that we will not retreat into a general scepticism becausesomeissues arebeyond human resolution. The same chapter makes it clear that Locke does not take thethought that there are areas in which we cannot expect to haveknowledgeto imply that inall such areas we must expect to remainignorant,and that he is as interested in caseswhere certainty is not possible for us but in which we may have reasonable beliefs. Hencehis announced programme, which is ‘to enquire into the Original, Certainty, and Extentof humane Knowledge; together, with the Grounds and Degrees of Belief, Opinion, andAssent’. Hence too a feature of theEssay,that where others might see their inability tosolve some problem arising from their overall position on some topic as at least a primafacie objection to that position, Locke may see such difficulties as simply confirming thatour powers of comprehension are limited. Sometimes this may strike the tough-mindedcritic as simply dodging the issues that matter, but this is certainly not Locke’s attitude.So far, then, we know something of Locke’s purpose, but nothing of his strategy forachieving it which he sets out in I.i.3 as being, first, to ‘enquire into theOriginalof thoseIdeas,Notions, or whatever else you please to call them, which a Man observes, and isconscious to himself he has in his Mind; and the ways whereby the Understanding comesto be furnished with them’; then ‘to shew, whatKnowledgethe Understanding hath bythoseIdeas’; and finally to ‘make some Enquiry into the Nature and Grounds ofFaith,orOpinion’. However, while this may seem superficially clear, it in fact gives only animperfect guide to the overall structuring of theEssay,and it leaves certain questionsunanswered, one of these being precisely what Locke means by ‘idea’. This question hasvexed commentators ever since, who have not been greatly helped by the knowledge thatLocke inherited the term and some of the obscurities that go with it. Locke offers somesort of explanation in I.i.8, but the overall impression one gets is that it strikes him as justobviousthatwe have ‘ideas’ in our minds—the ideas of, for example, whiteness,thinking, an elephant or an army—and that he is not concerned with what an ideais. Thusthe important question becomes simply how wecome byour ideas. His reply—‘To this Ianswer, in one word, FromExperience’ (II.i.2)—is what has marked him out as an‘empiricist’, or as one committed, using a dictionary definition, to ‘The theory whichregards experience as the only source of knowledge’. One need not quarrel with thisascription—Locke goes on to stress that ‘In that, all our Knowledge is founded; and fromthat it ultimately derives it self—so long as one appreciates that, for Locke, it isexperience that is the origin ofideas,or what he calls the ‘materials’ of knowledge, andthat when, in book IV, he considers ‘whatKnowledgethe Understanding hath by thoseIdeas’, it might seem as appropriate to judge him a rationalist. Nor should we assume thatbecause Locke takes it as evident that we have ‘ideas’, or conceptions, such as those of anelephant, existence or God, there is nothing problematic about his talk of ‘ideas’. Lockeencourages us to take a relaxed attitude to them, and it would indeed be rash to assume atthe outset that they must beimagesas some have thought,4 but it would be just as rash toassume that questions don’t arise concerning them. For the moment, however, we mustjust be clear that Book II of theEssayis not concerned with knowledge and belief assuch, but with the ‘ideas’ that ground these. Locke will consider, for example, how wecome by the ideas of God and existence. If we haveknowledgethat God exists, this willemerge in Book IV.IIIThough Locke announces his programme at the beginning of Book I by saying that hisfirst concern will be with how we acquire our ideas, he in fact doesn’t address thisquestion directly until Book II. Instead, after the first chapter in Book I, which introducestheEssayas a whole, three chapters are devoted to what may strike the modern reader asa tiresome digression: an attack on innate principles. It is important to realize, then, Boththat the attack on innatism was deemed highly controversial at the time, and that thesechapters complement the rest of theEssay. Putting it simply, Locke’s positive claim thatall our knowledge derives from experience really amounts to a claim that no knowledgeis prior to it, and this would have been seen by his contemporaries as in itself denyingthat some knowledge is innate. The direct attack on innatism in Book I and the workingout of his empiricism in the rest of theEssayare thus two sides of one coin, and bothwere judged subversive, even by those who insisted that he attacked too crude a versionof innatism, leaving more sophisticated versions intact. Whatever precisely theymeantbythis, many felt it imperative to hold that certain principles which Locke calls ‘practical’,including the fundamental principles of morality and religion, were innate if theirauthority was not to be jeopardised, and many were convinced that certain ‘speculative’principles, for example ‘Whatever is, is’ must equally be ‘native’ to the mind, and indeedfundamental to knowledge in general. When, much later in theEssayLocke attacks thescholastic notion that ‘all Reasonings areex praecognitis, et praeconcessis’, explainingthat this means that certain supposedly innate maxims are ‘those Truths that are firstknown to the Mind’ and those upon which ‘the other parts of our Knowledgedepend’ (IV.vii.8), we have an illustration of how Locke could see himself as ‘removingsome of the Rubbish, that lies in the way to Knowledge’. We can also see that his attackon innatism was not peripheral to his programme.In the event Locke devotes one chapter to the supposedly innate speculative truths, oneto practical truths, and, finally, one largely to innate ideas on the basis that if, forexample, the knowledge that God is to be worshipped were innate, the ideas of God andworship would have to be innate too. That the ideas are not innate Locke takes to beevident. As he says,If we will attentively consider new bornChildren,we shall have little Reason,to think, that they bring manyIdeasinto the World with them. For, bating,perhaps, some faintIdeas,of Hunger, and Thirst, and Warmth, and some Pains,which they mayhavefelt in the Womb, there isnotthe least appearance of anysettledIdeasat all in them.(I.iv.2)Infants, then, patently lack them, but so too do some adults, both of which would beimpossible were they innate.To the modern reader, one problem with Locke’s polemic is likely to be that what hetakes to be obvious here—and he takes much the same line on supposedly innateprinciples—will seem just that, obvious, so that his attack on innatism is likely to seemunnecessarily prolix, particularly given that it might seem that nobody could seriouslyhave held the view he attacks. Thus Descartes, for example, who we know did hold thatthe idea of God was innate, surely didn’t believe that every infant, or indeed every adult,has the idea consciously formed in his mind. To be fair, Descartes can be found writing ina way that suggests that the idea will be there, fully formed but not attended to—theinfanthas in itself the ideas of God, itself, and all truths which are said to be selfevident;it has these ideas no less than adults have when they are not payingattention to them, and it does not acquire them afterwards when it grows upbut elsewhere he takes the view that what is innate is, rather, a capacity or disposition,comparable to a natural disposition to gout.5 Both notions are designed to take account ofthe fact that the infant does not entertain conscious thoughts about God, which mightseem to cut the ground from under Locke’s objection. In fact, it is clear that neither movewould trouble Locke. His tactic throughout the polemic is to take the claim that certainitems of knowledge (or ideas) are in the mind from the first quite literally, so that theinfant for example should be conscious of them, and then to represent any watering downof the doctrine as a retreat into obscurity or triviality. For example, dealing with thenotion that what is innate is a natural capacity, he argues that ‘if the Capacity of knowingbe the natural Impression contended for, all the Truths a Man ever comes to know, will,by this Account, be, every one of them, innate’, for, trivially, we must always have hadthe capacity to acquire any knowledge we eventually acquire, so that ‘this great Point willamount to no more, but only to a very improper way of speaking’ (I.ii.5). At this level,indeed, Locke’s attack on innatism is quite effective; it was clearly necessary, for in oneform or another the doctrine that there was innate knowledge was widely received; andeven if it did not once and for all end any talk of innate impressions (Leibniz for oneattempted to defend it against Locke) it increasingly lost its hold. It has been claimed that‘there has been no trace of it in recent thought’.6IVAs already stated, Book I complements the rest of theEssayin the sense that the denial ofinnate knowledge is merely the negative face of the positive claim announced at thebeginning of Book II. It follows that Locke himself sees the direct attack as in a waysuperfluous to his programme (see I.ii.i), though, by the same token, he sees that theattack in Book I will be ‘more easily admitted’ once it has been shown how experiencedoes provide a sufficient basis for our ideas (II.i.1). What follows in the rest of theEssayis thus, in part, an account of how experience gives rise to our ideas, and the knowledgebased on them, though, and in a way more importantly, it is an exploration of theimplications of this account. The fascination of the work as a whole thus lies in large partin what Locke has to say on a variety of issues, ranging from what sorts of achievementwe can expect in natural science, to the nature of the human mind and its relation to thebody, personal identity, the status of moral truths, and whether God’s existence can beproved. The emphasis throughout is of course epistemological—on what we can knowand what we can reasonably surmise in this or that area—but firm conclusions are drawn,including that there is a God and that this can be proved. For the moment, however, wemust stay with Locke’s basic empiricist claim.This is that all our knowledge derives from ‘experience’, but the gloss Lockeimmediately puts on this is important for three reasons. First, he makes it clear that therearetwosources of experience, sensation and what he calls ‘reflection’, which provides themind with ideas of its own operations, such as perception, thinking and doubting; secondbecause the derivation of an idea from experience is not seen as always a simple matter(on the model of deriving the idea of green from seeing green things), in that it will benecessary to take ‘a full survey’ of our ideas, including ‘their several Modes,Combinations, and Relations’, or as they are ‘with infinite variety compounded andenlarged by the Understanding’ (II.i.5); and, third, because, from the outset, the existenceof external objects is apparently taken for granted. Ideas of sensible qualities, such as thatof yellow, are thusintroducedas those conveyed into the mind ‘from externalObjects’ (II.i.3), and it is not until much later (IV.xi) that Locke dwells on the notion,which he even there treats as absurd, that there may be no external objects at all. Thismay seem surprising given that scepticism on this matter was very much in the air at thistime, and indeed that, since Berkeley at least, we have been encouraged to see Locke’sown philosophical position as positively inviting scepticism, so it needs stressing thatLocke himself shows no such anxieties. It is worth noting too that the examples of ideasderived from sensation given in II.i.3—yellow, white, heat, cold, soft, hard, bitter,sweet—are all what Locke will call ‘simple’ ideas, and that this is no accident. It is anessential part of what is known as Locke’s ‘compositipnalism’ that ‘simple’ ideas are as itwere the basic data, and that, given these, other, complex ideas can be formed, such asthose of gold, a centaur or a lie. It would be possible to spend quite a lot of time on thedistinction between simple and complex ideas, for there is no doubt that it is, at best, notas clear and straightforward as Locke seems to suggest and it has even been argued thathe tacitly abandoned it when it becomes embarrassing. Here we can only note thatchapters ii to viii of Book II are officially devoted to ‘simple’ ideas, that chapters ix to xicover various faculties and operations of the mind, and that from chapter xii on Locketurns to ‘complex’ ideas. That it is not, however, the issue of Locke’s basiccompositionalism that is of most interest or importance is suggested by the fact that manyof the topics that have most engaged readers then and since can be examined withoutpaying special attention to it.7 There is much in Book II we could linger on, and somethings that we shall.Book II of theEssayis in fact a mine of interesting and often important material,though the significance of much of it can only be fully understood in terms of thephilosophical concerns of the time, and even then the significance may not beimmediately recognizable, at least from the titles of the relevant chapters. Thus, theunpromising title of chapter xiii, for example, is‘Of simple Modes; and first, of thesimple Modes of Space’,but it includes Locke’s rejection of the Cartesian claim that avacuum is inconceivable, building on a distinction between the ideas of body and spaceestablished in chapter iv, as well as observations on the notion of substance, though thiswill not be the main focus of interest until chapter xxiii. Similarly, chapter viii has theunexciting title‘Some farther Considerations concerning our Simple Ideas’,but it is herethat we find Locke’s classic defence of a distinction between primary and secondaryqualities. Chapter xxi—‘Of Power’—includes a long discussion of human freedom; whileif we want to know how Locke takes the idea of God to be derived from experience, wemust look to four sections (33–6) almost hidden away towards the end of chapter xxiii.One could go on. Suffice it to say that, though theEssayas whole can strike one asrambling and diffuse, so that it becomes tempting to focus on the isolated topics whichinterest one, the work is better approached as a whole. Certainly, one needs to be alert tovarious developingthemes.VJust which themes are the most important must be to some extent a matter of opinion, andit is certainly true that what was judged most significant in Locke’s own day often differsfrom what has most exercised commentators more recently. This is hardly surprising,given Locke’s successes in removing what he saw as rubbish, which has meant that whatseemed to be important issues then have often ceased to exercise our minds since. Indeedthis may be the point to reiterate that in his own time Locke was often regarded assubversive,8 to the extent that some were inclined to suspect a not too well hiddenagenda. Stillingfleet or Leibniz could be cited here, but as good an example as any wouldbe another critic, Thomas Burnet, who devoted the first of three sets of publishedRemarkson theEssayto polite queries, but who concluded the third set by laying hiscards on the table and accusing Locke of not doing the same. The ‘key’ to decipheringLocke’s philosophy, indeed ‘the mystery aimed at all along’, is he suggests, thesupposition ‘that God and matter are the whole of the universe’. For Burnet, Lockeemerges as a deist, whose system provides for only an inadequate conception of both Godand the human soul. Shortly afterwards Berkeley was yet another to be struck by what hesaw as dangers implicit in Locke’s philosophy, but he was only one of many to be struckby Locke’s suggestion that matter might think. In fact, this particular suggestion occurs injust one section (IV.3.6), where Locke presents it only as an illustration of how limitedour knowledge is, and it would be rash to assume that there was a hidden agenda.However, the suggestion can be seen as a natural culmination of much that had gonebefore. It provides one key, though certainly not the only one, to unravelling some of theintricacies of theEssay.Thus the modern reader approaching even the first chapter of Book II may find it oddthat, in defending his claim that we are dependent on experience for our ideas, Lockedevotes many sections to an attack on the notion that the soul always thinks, either priorto an individual’s first sensory experiences, or during the course of his life. For, whilethere is an obvious connection here with Locke’s basic empiricist programme and hisrejection of innatism, what we may miss is the significance of the fact that Locke is alsoundermining the notion that thought is the soul’sessence. For Descartes at least, thisnotion was central to a proof that the soul was immaterial, so it is unsurprising that thoseimmersed in this tradition could see Locke’s attack on it, and indeed his attack oninnatism too, as closely connected with doubts about the soul’s immateriality. Indeed, thedangers could only become more apparent when, in II.xxiii, Locke makes it clear that weare ultimately in the dark about what the soul’s essence is. Here there is alink between hisobservations oncorporealsubstance, or the supposed substratum of sensible qualities,which we shall return to, and his comments on the substance underlying mentaloperations, when he claims that, like the substance of body, ‘The substance of Spirit isunknown to us’ (sect. 30). Admittedly, chapter xxvii, which was added in the secondedition, is for the most part devoted to an account of personal identity which attempts todisentangle the idea of the continuance of apersonfrom that of the persistence ofanyparticular sort of substance, and he will hold in IV.iii.6 that our belief in immortality isnot threatened whatever the nature of the soul. But the upshot is that Locke can find noproofof the natural immortality of the soul. For Locke, of course, this emerges as oneillustration of the limits of human knowledge. For many readers, the dangers were clear.9VIThere is, however, a much more dominant theme running through theEssay,whichconnects indeed with the last but underlies much that Locke says in Books II, III and IV,for many of Locke’s concerns centre on what might best be described as an explorationof the implications of the corpuscular science associated in particular with Boyle. InBook II, two topics to which this concern is clearly very central are his treatment ofprimary and secondary qualities in II.viii, and of our idea of substance in II.xxiii. Bothhave given rise to much discussion, and indeed—with the possible addition of II.xxvii(on personal identity)—these have probably been the most widely discussed chapters inBook II. They are, I think, best treated together, though very often they have been treatedseparately.Certainly, that Locke’s concern in II.viii is with the implications of the new sciencecan hardly be denied given what he himself says in section 22 where, after noting that “Ihave in what just goes before, been engaged in Physical Enquiries a little farther than,perhaps, I intended’, he adds that this wasnecessary, to make the Nature of Sensation a little understood, and to make thedifference between the Qualities in Bodies, and theIdeasproduced by them inthe Mind,to be distinctly conceived, without which it were impossible todiscourse intelligibly of them.Nor is it deniable that the natural philosophy Locke has in mind here is the corpuscularsystem, which, as Locke explicates it, entails that our ideas of colours, odours and tastesfor example correspond to secondary qualities, which are but powers in objectsdepending on ‘the Bulk, Figure, Texture, and Motion of their insensible parts’ (sect. 10).There is indeed much that is problematic in Iviii—for example the implications of hisclaim that our ideas of primary qualities, but not of secondary qualities, are‘resemblances’ of them, but the centrality of the new science to what Locke says isevident. What thisopposesis, basically, Aristotelian science, which would account forour perception of colours for example by reference to theformsof the colours in theobjects, so it seems reasonable to suppose that when Locke complains thatMen are hardly to be brought to think, thatSweetness and Whiteness are notreally in Manna;which are but the effects of the operations ofManna,by themotion, size, and figure of its Particles on the Eyes and Palate(sect. 18)the men he has in mind will include, not just ordinary folk, but supporters of a soon to bedefunct metaphysics.Even if we accept that, however, there is much that could be discussed. It might beasked, for example, what right Locke had to appeal to the new science for the distinction,given that the new science remained controversial; how, if the ‘minute parts’ which arecentral to the story are ‘insensible’, we could know anything at all about them; and howLocke’s view that some of our ideas are, and some are not, ‘resemblances’ of qualitiescould ever be established, given, what he will say later, that ‘the Mind…perceivesnothing but its ownIdeas’. Here, so far as the first of the questions is concerned, it mustsuffice to say that Locke’s general attitude to the corpuscular hypothesis is that it is thebest available (IV.iii.16); that, so far as the particles being ‘insensible’ goes, Locke takesthis insensibility to be a merely contingent matter, which would be overcome if oursenses were more acute; and that, ultimately it seems, his claims about which ideas areand which are not resemblances of qualities could be justified only in terms of anacceptance of the underlying scientific theory. All we need to add perhaps is that thisacceptance was not simply dogmatic. Given this theory, and the distinction between ideasthat goes with it, facts such that the same water can feel warm to one hand and cool to theother could be accounted for (II.viii.21).10 The question of what exactly Lockemeanswhen he says that ‘the Mind…perceives nothing but its ownIdeas’, is perhaps better leftfor a while. There is more than one way of understanding it.For the moment it is more important that we note that notions that figure prominentlyin II.viii do re-emerge in II.xxiii, where the attention of commentators has often beenfocused more on what Locke says about our idea of substancein general,particularly inthe earlier sections, than on the topic suggested by the title, which is ‘Of our ComplexIdeasof Substances’. On the first of these issues Locke talks of our “obscure and relativeIdeaof Substance in general’ as ‘something…standing under’, or supporting qualities;but on the second, where his concern is with our ideas of particularsortsof substancessuch as gold, his claim is that we form these ‘by collecting such Combinations of simpleIdeas,as are by Experience and Observation of Men’s Senses taken notice of to existtogether, and are therefore supposed to flow from the particular internal Constitution, orunknown Essence of that Substance’. As is so often the case with Locke’sEssay,therehas been no clear concensus on precisely what is going on in this chapter,11 but there isgrowing agreement that what he is struck by is the unhelpfulness of philosophicaltheorizing in terms of the abstract categories ofsubstanceandaccident,even though hesees our ordinary ways of talking about objects as reflecting an idea of ‘something’underlying theobservablequalities of things. Suggestions such as that if we had ‘Sensesacute enough’ we would ‘discern the minute particles of Bodies, and the real Constitutionon which their sensible Qualities depend’ (sect, 11) give us a very obvious link withII.viii, and underwrite the view that, for Locke, speculations about substance in generalbring us to the area of ‘obscure terms and useless questions’, contrasting with theintelligible theorizing of the new science. It remains the case, however, that we have herean area where, in Locke’s reasonable seventeenth-century view, the limits of humanunderstanding are clear. Had we ‘Senses acute enough’ we would indeed be able topenetrate into the inner natures of things, but the truth is that we don’t.VIIThe programme announced in I.i.3 would lead one to expect that, having dealt with the‘materials’ of knowledge, Locke would next consider knowledge itself. But, as he says atthe very end of Book II, he has been struck by the fact that ‘there is so close a connexionbetweenIdeasand Words…that it is impossible to speak clearly and distinctly of ourKnowledge…without considering, first, the Nature, Use, and Signification of Language’.In Book III, therefore, he gives us his account of language.The basic picture he offers in the first two chapters in Book III is fairly simple. Wordsare not necessary for thought itself, but primarily in order for men to communicate theirthoughts to others, or ‘to record their own Thoughts for the Assistance of their ownMemory’ (III.ii.2). Words, or significant sounds, are therefore signs of our internalconceptions, and can ‘properly and immediately signify nothing but theIdeas,that are inthe Mind of the Speaker’ (sect. 4). Men do, however, give them a secondary or ‘secret’reference in that, precisely because language is used to communicate, they assume thatthe words they use to signify their own ideas mark the same ideas in the minds of thosethey converse with, while, ‘BecauseMenwould not be thought to talkbarelyof their ownImaginations, but of Things as they really are’ they often take them to stand for‘thereality of Things’(sect. 5). Locke’s cautionary words at this point—‘it is a perverting theuse of Words, and brings unavoidable Obscurity and Confusion into their Signification,whenever we make them stand for any thing, but thoseIdeaswe have in our ownMinds’—may strike us as simply perverse—surely if I say ‘John is bald’ I do mean torefer to John himself, but the implications of the remark become much clearer later.Sticking for the moment with the opening chapters, it is necessary only to add that Lockeis very conscious that most words do not signify only particular, individual things. Manystand for general ideas.There are, however, nine chapters still to come in Book III, and it must be said at oncethat here, as quite often in theEssay,one becomes conscious of a mismatch betweenwhat probably most interests Locke himself—the points he most wants to get across—and what has most caught the attention of critics and commentators since. This canindeed be illustrated by the fact that Book III ends with three chapters on the ‘abuses’ and‘imperfections’ of words, and the ‘remedies’ for these, which are clearly important toLocke, given his overall aims, though they have concerned commentators less. It is,however, also apparent even if one turns to chapter iii, which is certainly the most widelydiscussed. It is entitled‘Of General Terms’.Clearly the topic of general terms, and the general ideas which they signify, isimportant to Locke, if only because, as will become plain in Book IV, most of ourknowledge will be found to consist in general propositions; but, since Berkeley at least,what has most caught the attention of commentators has been his account of what mightbe termed the mechanics of abstraction, or the process by which Locke takes it we formgeneral ideas. Taking the word ‘man’ as an example, Locke holds that children will startwith the ideas of individuals—Peter, James, Mary and Jane—and then, having notedcertain resemblances, frame an idea in which they ‘leave out…that which is peculiar toeach, and retain only what is common to them all’. Berkeley was to devote the bulk of theIntroduction to thePrinciplesto attacking abstraction, insisting, for example, that ‘theidea of man that I frame to my self, must be either of a white, or a black, or a tawny, astraight, or a crooked, a tall, or a low, or a middle-sized man’ and that ‘I cannot by anyeffort of thought conceive the abstract idea above described’, and his criticisms haveoften focused minds on this aspect of Locke’s thought. By contrast, what seems to mattermost to Locke is the distinction between real and nominal essences which he spells outlater on in the chapter, to which the account of abstraction is a prolegomenon.Certainly, this distinction brings us right back to a dominant theme which we havealready looked at, for ‘the real Essences of corporeal Substances’ are located in the ‘real,but unknown Constitution of their insensible Parts, from which flow those sensibleQualities, which serve us to distinguish them one from another’ (sect. 17). And thedominant notion that emerges now is that we rank things into sorts, neither on the basis ofthese real essences, which we do not know, nor on the basis of the real essences of thescholastics, which they think of as ‘a certain number of Forms or Molds, wherein allnatural Things, that exist, are cast, and do equally partake’ (ibid.), but rather according towhat Locke calls ‘nominal’ essences. These are, indeed, the abstract ideas alreadycovered, but the crucial thought is that we categorize things into sorts on the basis ofcertainobservedproperties which we choose to associate as constituting one sort.Negatively, then, the dominant concern of the chapter is another piece of rubbishremoval,in this case the ‘real essences’ or ‘forms’ of the schools;12 positively it is anaccount of classification according to which ‘the sorting of Things, is the Workmanshipof the Understanding’ (sect. 12). More generally, and as we shall see, the accountprepares the way for what Locke will say about the science of nature in Book IV.There is of course much more in Book III, including treatments of the names of simpleideas in chapter iv, of the names of mixed modes and relations (‘adultery’ and ‘gratitude’are among the examples) in chapter v, of the names of substances again in chapter vi, andof particles (words such as ‘but’ and the ‘is’ of predication) in chapter vii, but this bookconcludes with the three chapters on remedying ‘abuses’ and ‘imperfections’. Recallingthe concern Locke expressed in his Epistle to the Reader about ‘the learned but frivoloususe of uncouth, affected, or intelligible Terms’, we can understand that these chapters arenot peripheral to Locke’s purposes, and his reference here to ‘gibberish’ such as theEpicurean notion of ‘endeavour towards Motionin their Atoms, when at rest’ (III.x.14)can serve as just one example of the sort of thing he has in mind. In fact he casts his netwide. His observation that, in common use, ‘body’ and ‘extension’ stand for distinctideas, but that ‘there are those who find it necessary to confound their signification’ (sect.6) is an obvious reference to the Cartesians.13VIIIGiven that one of the main aims of theEssayis to determine the scope of humanknowledge, it perhaps comes as something of an anticlimax that, in the event, Lockeallows very little that he will count as knowledge. That this will be so is stronglysuggested by the very first chapter in Book IV where he defines ‘knowledge’ as‘theperception of the connexion and agreement, or disagreement and repugnancy of any ofour Ideas’,giving as the first two examples‘White is not Black’and‘the three Angles ofa Triangle are equal to two right ones’. Locke in fact holds that the first of these involvesone of four sorts of agreement or disagreement on which knowledge can be based—‘Identity,orDiversity’—while the second is based on what he calls‘relation’. The othersorts of perceived agreement are ‘Co-existence, ornecessary connexion’ (one examplegiven is that‘Iron is susceptible of magnetical Impressions’,which, in so far as we knowit, will turn out to be construed as what we would now term an analytic proposition), and‘Real Existence’,the one example given in IV.i being‘GOD is’. When we find that inchapter ii he tells us that the primary ways of knowing are ‘intuition’ (anyone who hasthe two ideas will simply see that white is not black) and ‘demonstration’, of whichmathematical proofs are the favoured model, the strong rationalist streak in Lockebecomes apparent. Indeed, for him, ‘intuition’, or self-evidence, lies at the root of nearlyall he recognizes as ‘knowledge’, for demonstration turns out to be based on nothingmore than a series of intuitions. A good illustration of how this is supposed to workwould be the series of supposed intuitions which he offers in IV.x as constituting ademonstration that God exists.Locke, then, offers a very restrictive account of ‘knowledge’, and as the chaptersproceed we find as much attention being given to things we cannot hope to know withcertainty as to what we can. Examples of things lying beyond the scope of our knowledgethus turn out to include that man cannot be nourished by stones (IV.vi.15)—theexplanation here being that our idea of man is that of ‘a Body of the ordinary shape, withSense, voluntary Motion, and Reason join’d to it’ and we can neither intuit nordemonstrate by our reason any ‘necessary connexion’ between that and what will nourishhim—and that opium will make a man sleep (IV.iii.25), but these could be multiplied.The proposition that gold is malleable for exampleisindeed certainly known to be true,but only if, as Locke puts it, ‘Malleablenessbe a part of the complexIdeathe wordGoldstands for’. If we happen not to include malleability in the definition of gold, or in theabstract idea, this again is something that cannot certainly be known (IV.vi.9). As he putsit in IV.viii.9,the generalPropositionsthat are madeabout Substances, if they are certain, arefor the most part but trifling,and if they are instructive, are uncertain, and suchas we can have no knowledge of their real Truth, how much soever constantObservation and Analogy may assist our Judgments in guessing.There are indeedsomeareas where Locke’s insistence that we lack ‘knowledge’ is, if notuncontroversial, at least such as to reflect a not unreasonable caution, as for example hisdenial that we know that matter cannot think, but equally there are many that seemsurprising. If I am not now perceiving any men, for example, Locke will deny that I‘know’ there are other men in the world (IV.xi.9).One question that arises here, then, is precisely why Locke tolerates an account ofknowledge that is as restrictive as this. And here no doubt at least part of the answer mustbe that he simply accepts a tradition whereby ‘knowledge’ does require a very highdegree of certainty, and is indeed tied to the notion of necessity. However, this judgementmust be tempered by three further observations. One is that, for all his parsimony when itcomes to recognizing ‘knowledge’, he does allow some items that, to us, may seem lesscertain than they did to him. The second is that in some cases where he is bound to saywe do and perhaps always will lack ‘knowledge’, he is still guided by a view of whatacquiring knowledge in these cases would be like. And the third is that, though he seesthat, with the requirements for ‘knowledge’ set this high, our ‘knowledge’ will be verylimited, he also insists that what we are then bound to call ‘probability’ may be of a veryhigh order indeed. These three points are essential to an understanding of Locke’s overallposition, so I shall elaborate on them briefly in turn.First, then, it is indeed true that Locke denies that we ‘know’ certain things we wouldnormally suppose we knew, but what we also find is that there are two areas offundamental importance in which he believes demonstrability is attainable. The obviousexample here is his supposed proof of the existence of God which, though flawed, hetook to be a sound demonstration, but we should note too his repeated claim that‘Morality is capable of Demonstration,as well as Mathematicks’ (III.xi.16, cf. IV.iii.18,IV.iv.7 and IV.xii.8). To be sure, Locke never claimed to have developed the system heenvisaged, but the mere fact that he thought it possible in principle is significant. For if,starting from God’s existence, and the supposed self-evidence of a creature’s obligationsto his creator, man could come by certainty in this area at least, ‘knowledge’ wouldcertainly transcend the trivial. As he put it as early as I.i.5,How short soever [men’s] Knowledge may come of an universal, or perfectComprehension of whatever is, it yet secures their great Concernments, thatthey have Light enough to lead them to the Knowledge of their Maker, and thesight of their own Duties.Indeed, the second point connects with this, for if Euclidean geometry is seen asproviding the model for a demonstrative morality, it is also the model of what it would belike to have certainty in natural philosophy. For here, Locke’s insistence that we don’t forexample ‘know’ that hemlock will always kill is combined with thoughts about whatwould be knowable to one whocouldpenetrate into the real essences of substances.Hence his observation in IV.iii.25 that could we but penetrate into the internal structureof things ‘we should know without Trial several of their Operations one upon another, aswe do now the Properties of a Square, or a Triangle’ (IV.iii.25). His assertion that ‘Couldany one discover a necessary connexion betweenMalleableness,and theColourorWeightofGold…he might make acertainuniversal Proposition concerningGoldin thisrespect’ thus goes along with pessimism about the possibility ofourdiscovering any sucha connection, but also with a view about what such a discovery would be like. As he hasit, ‘Thatall Gold is malleable,would be ascertainas of this,The three Angles of allright-lined Triangles, are equal to two right ones’ (IV.vi.10).The strong rationalist streak in Locke is thus evident here, in his pessimism aboutouracquiring much by way of ‘knowledge’ in this area, quite as much as it is in his optimismabout the possibility of a demonstrative morality, but it also connects with his lack of anydeep concern that our ‘knowledge’ is, on his view, limited. And this brings us to the thirdpoint, which concerns the stress he put on the notion that ‘probability’ is not to bedespised. For, on Locke’s account, to deny that I ‘know’ that man cannot be nourished bystones turns out to be no more than to assert that this truth is not self-evident ordemonstrable, not that ‘constant Observation and Analogy’ don’t justify the high degreeof assurance we in fact have, let alone that there are reasonable grounds for doubt. Thetone here was in fact set back in I.i.5 with his observation that we should ‘notperemptorily, or intemperately require Demonstration, and demand Certainty, whereProbability only is to be had, and which is sufficient to govern all our Concernments’,and the same note is struck later, in IV.xi.10. A truth may be ‘plain and clear’, though notstrictly ‘known’.IXIt would thus be a mistake to describe Locke as a sceptic, at least solely on the basis thathe denies us ‘knowledge’ in certain areas where we would normally suppose we had it.14Admittedly there are areas in which he thinks our lack of understanding goes deep—‘Wehave theIdeasofMatterandThinking,but possibly shall never be able to know, whetherany mere material Being thinks, or no’ (IV.iii.6), and we simply don’t understand forexample ‘how anysize, figure,ormotionof any Particles, can possibly produce in us theIdeaof anyColour, Taste,orSoundwhatsoever’ (IV.iii.13)—but in matters that affectour practice, such as that stones will not nourish us, all we lack is demonstrativeproofs.The most that can be said is that there may be one particular area where Locke shouldhave been more sceptical than he was. This brings us back to the area of ‘real existence’,and in particular to sensitive knowledge.The truth here is that, though when he introduces his account of knowledge in IV.i theonly example Locke gives of our knowledge of real existence is our demonstrativeknowledge that God exists, he in fact recognizes not only our supposedly intuitiveknowledge of our own existence (IV.ix.3), but knowledge of the existence of externalobjects. Admittedly, the scope of this knowledge turns out to be very limited—broadly I‘know’ that an object exists only when I actually sense it—but all the same it has oftenbeen questioned whether Locke is entitled to claim even this. There are two difficultieshere. One is that Locke defines ‘knowledge’ as the perception of the agreements anddisagreements ofideas,and it seems doubtful that this can allow for ‘knowledge’ of theexistence ofanythingwhich is not itself an idea, whether God, oneself, or any externalthing; and the second is whether he is entitled to claim even an assurance of the existenceof bodies, given his apparent belief that we never perceive any. This second difficulty isat best tangentially connected with the definition of ‘knowledge’, and would arise evenwithout it. His notorious comment in IV.iv.3 that ‘the Mind…perceives nothing but itsownIdeas’ raises it very forcibly, while bringing us back to the topic of Locke’s idea of‘idea’.On the first of these supposed difficulties, all that can be said here is that it seems thatLocke himself did not think that his definition ruled out any knowledge of ‘realexistence’, in that he supposed the existence of God at least could be demonstrated byattending solely to our ideas. What is supposedly established here is, apparently, still arelationship between two ideas, those of God and of real existence. He makes a similarpoint to Stillingfleet in defending his position on sensitive knowledge,15 though in theEssayitself there are indications that he does have some misgivings about whether,strictly, this should countas ‘knowledge’ at all.16 Even there, however, he certainlyclaims that in this area ‘we are provided with an Evidence, that puts us past doubting’, sothe real issue is whether he was entitled to claim even that. At this stage it is the seconddifficulty that becomes acute. Very often, traditionally even, Locke has been seen asadopting a Representative Theory of Perception which positively invites scepticism inthis area. If ‘the Mind…perceives nothing but its ownIdeas’ it seems we donotperceivetables and chairs, and this appears to make their existence genuinely questionable. ThatLocke himself shows little sign of anxiety about this hardly lessens the difficulty.Unfortunately we can do little more than note this apparent problem, apart fromobserving that it is of some historical importance (Berkeley’s idealism will have it as itsstarting-point) and that there has been much controversy on just what view of perceptionLocke is committed to. Whether those commentators are right who claim that Locke’sideas of sense are ‘objects’ or ‘entities’, and indeed the only objects of which we are everaware, rather than ‘perceptions’, or states of awarenessof the things themselves,liesbeyond the scope of an introductory essay. What must at least be conceded, however, isthat there is undeniably a strong streak of what might be called ‘perceptual realism’ inLocke; that in many passages he does talk of perceiving the external things, and that eventhe claim that ‘the Mind…perceives nothing but its ownIdeas’ can be interpreted in thelight of his talk of ideas as being ‘found’ in the things themselves.17 Perhaps, but onlyperhaps, Locke is simply inconsistent, but claims such as that ‘we immediately by ourSenses perceive inFireits Heat and Colour’ (II.xxiii.7) and suggestions that what we donotperceive is the corpuscular structuring on which these qualities depend aresignificant. A strong case can be made for the view that the key to Locke’s thinking liesthere.XIt goes without saying that there is much in Locke’sEssaythat has not been discussedhere. That however is inevitable. His interest is perennial and his importance clear, butjust what most interests a particular reader will depend on a number of factors. To hiscontemporaries his attacks on what he saw as ‘rubbish’ lying in the way to knowledgewere of genuine significance, while the perceived implications of his epistemology fortheology could and did cause deep concern. The importance he himself attached to, forexample, his attack on ‘enthusiasm’ in religion in IV.xix is, though it was only introducedin the fourth edition, evident from its vigour, but the chapter is omitted from a recentabridgement. We now know that Berkeley was soon to attack the very notion of ‘matter’,or of bodies existing without the mind, and though he certainly wasn’t just addressingLocke, Locke has often been seen as his prime target. Locke’s doctrines concerning ideashave thus come to be seen as a stepping-stone to Berkeley’s idealism and indeed toHume’s scepticism. His accounts of abstract ideas, primary and secondary qualities,substance and so on have been examined over and over again in the light of Berkeley’scriticisms, while others see them as significant in their own right. Again, Locke’s accountof personal identity has been no more than touched on here, but he was the first to raisethe issue in the form in which it continues to be discussed today, and his contribution isadmired and, still, widely discussed. Other features of his position have been warmlypraised—one commentator claims that he handles the notion of real essence ‘almostflawlessly’18—yet often he has been used for target practice, and Gilbert Ryle oncesuggested, though perhaps not wholly seriously, that ‘nearly every youthful student ofphilosophy both can and does in about his second essay refute Locke’s entire Theory ofKnowledge’.19 I imagine that few, certainly few who have delved at all deeply into histhinking, would now second that sort of judgement, but for all that the correctinterpretation of his position remains a matter of controversy at almost every point. Thisis perhaps hardly surprising, for Locke stands at a crucial point in the development of thehistory of philosophy, epitomizing the shift from ways of thinking that have becomelargely foreign to us, to ways that seem familiar. University courses entitled ‘History ofModern Philosophy’ thus customarily have Locke’sEssayas their first text originallywritten in English. His problems have become, in a sense, our problems. Yet we findthem emerging from a background that has become less familiar. Getting the most out ofLocke’s philosophy will therefore involve using hindsight, for we know its fruits, but alsounderstanding the world from which it emerged. It is only if we do both that Locke’s truegenius can be seen.NOTES1 References to the Essay are to the Clarendon Edition, [3.3], and cite book, chapter andsection number. Except in the case of the Epistle to the Reader the italics have been leftunchanged.2 In his John Locke ([3.22], 31–5), first published in 1937, R.I.Aaron noted Leibniz’s commentthat Locke ‘writes obviously in the spirit of Gassendi’, and argued that the influence ofGassendi’s thought on him was considerable. Further discussions include Kroll, [3.52], andMichael, [3.56].3 Aaron, [3.22], 27. However, both he and Gibson, [3.25], 236–41, also draw attention toimportant differences of view. For one thing, most of the Cambridge Platonists held thatthere were innate ideas, and as Gibson notes ‘nothing, Cudworth declared, could moredirectly promote atheism than the Aristotelian maxim, “Nihil est in intellectu quod non fitprius in sensu”’.4 As will emerge, for Locke we have ideas in sense experience, and also in thinking andreasoning. The question of whether ideas are images can therefore emerge at two levels.Some have held that he takes the immediate object of perception when we see or otherwiseperceive an object to be itself an image, or an entity which somehow stands proxy for theobject, while others seem more concerned with whether the ideas that we might now callconcepts are images. No doubt the relationship between these two issues is important, but itseems fair to say that most often it has been his view of sense perception that has exercisedhis readers, though it is ideas as concepts that feature most prominently in the Essay. When,however, Ayers claims ([3.21], 1:44) that, ‘the grounds for holding him an imagist areconclusive’, it is clear from the context both that he regards this judgement as controversial,and that his eye is fixed on ideas as they function in thought. Certainly, the nature of Locke’sidea of ‘idea’ continues to be much discussed.5 For an examination of Descartes’s doctrine of innate ideas, which includes the relevantpassages, see Anthony Kenny, Descartes: A Study of His Philsophy, New York, RandomHouse, 1968, ch. 5.6 Mabbott, [4.26], 80. Even when this was published, however, a debate was in progress overNoam Chomsky’s claim that his work in linguistics vindicated the rationalists on this issue.This claim was controversial, and it was widely criticized. See, for example, D.E.Cooper,‘Innateness: Old and New’, Philosophical Review 81 (1972): 465–83.7 Which is not to say that nothing is lost. Aaron, [3.22], 110–14, and Gibson, [3,25], ch. 3, areamong commentators who have played down its importance, but for a survey which takes itseriously, see Stewart, [3.58]. Locke’s compositionalism and its historical background alsolooms large in, for example Schouls, [3.38], and Ayers, [3.44].8 This notion did not rest only on what he wrote in the Essay, nor simply on the issue I shallconcentrate on here. His publication of a work entitled The Reasonableness of Christianity in1695 fuelled doubts as to his orthodoxy, particularly on doctrines such as those of original sinand the Trinity, while his correspondence with Stillingfleet focused attention on the supposedtheological implications of the Essay.9 This is well documented by Yolton, [3.15], 148–66, cf. [3.40], ch. 1 and passim, and [3.41].If, from our standpoint it might seem absurd that Locke’s contemporaries made so much of asuggestion that is far from prominent in the Essay, we should be clear that things looked verydifferent then, as they did to Leibniz for example. His reaction is examined by Jolley, [3.37],who argues that ‘For all its apparent randomness and lack of direction, the New Essays onHuman Understanding is a book dedicated to defending the idea of a simple, immaterial andnaturally immortal soul’ (p. 7).10 This is among a number of phenomena instanced in II.viii. 16–21, which have, sinceBerkeley at least, often been read as revealing Locke’s acceptance of what is called ‘theargument from the relativity of perception’ to prove or demonstrate the subjectivity of certainsupposed qualities. For a quite different, and more plausible account, see Alexander, [3.35],124–9.11 See for example Ayers, [3.43], including the references given on p. 78, n. 2.12 This is just one of a number of references in the Essay to the substantial forms of the schools.For example, in IV.iv.13 Locke again protests the view that ‘there were a certain number ofthese Essences, wherein all Things, as in Molds, were cast and formed’. It is stronglyarguable that commentators who fail to attach due importance to Locke ‘s dissatisfaction withthis scholastic notion can only misunderstand many of Locke’s better knownpronouncements, including not only a problem he raises earlier in IV.iv—that of how we canknow that our ideas ‘agree with Things themselves’—and his answer to it as it relates to ourideas of substances, but also his insistence that words signify ideas, the account of knowledgegiven in Book IV, and even the content of II.xxiii. There too, in section 3, we find asignificant reference to the suspect ‘substantial forms’ of the schools. (For a brief account ofthe doctrine, as understood by Locke and his contemporaries, see Woolhouse, [3.33], sect.12.)13 These examples are of ‘abuses’, but Locke’s treatment of the ‘imperfections’ of words is alsoimportant. His initially puzzling insistence that ‘Words…can properly and immediatelysignify nothing but the Ideas, that are in the Mind of the Speaker’ underlies his analysis ofthe difficulties we get into with the names of mixed modes (such as ‘murder’) andsubstances, and the remedies for these. An illustration is a dispute between physicians hereports on in III.ix.16 over ‘whether any Liquor passed through the Filaments of the Nerves’.This was largely resolved when they saw that ‘each of them made [the term ‘liquor’] a signBIBLIOGRAPHYCollected Works3.1 In progress:The Clarendon Edition of the Works of John Locke,Oxford, ClarendonPress, 1975–.3.2The Works of John Locke,London, T.Tegg,et al.,1823, 10 vols.Editions of theEssay3.3 Nidditch, P.H. (ed.)An Essay concerning Human Understanding,Oxford, Clarendonof a different complex Idea’.14 References to Locke as a sceptical philosopher that are found in the literature are, however,not wholly unjustified if they are linked to his observations about the limits of humanunderstanding and, in particular, to his claims about our inability to penetrate into the realessences of things. The one point I want to insist on is that, for Locke, the claim that I don’t‘know’ for example that stones won’t nourish me does not entail suspension of judgement,nor any suggestion that there are reasonable grounds for doubt.15 Locke, [3.2], 4:360.16 Thus Locke’s account of the ‘degrees’ of our knowledge in IV.ii dwells on intuition anddemonstration, and he observes at the beginning of section 14 that ‘These two…are thedegrees of our Knowledge; whatever comes short of one of these, with what assurance soeverembraced, is but Faith, or Opinion, but not Knowledge’. On the face of it, this should rule outknowledge of the existence of things ‘without us’, for in the same section he admits that thisfalls short of ‘either of the foregoing degrees of certainty’. All the same, it ‘passes under thename of Knowledge’, and this is something Locke immediately endorses. Similarly, hisobservation in IV.xi.3 that in this area we have ‘an assurance that deserves the name ofKnowledge’ is not unnaturally read as conceding that he is making it ‘knowledge’ by specialdispensation.17 Locke’s only sustained treatment of our knowledge of the existence of things ‘without us’ isin IV.xi, so it should be noted that here as in other key passages (e.g. II.viii.12) there is nosuggestion that we do not perceive such objects. Indeed, it is said at the outset that it is ‘whenby actual operating upon him, it makes it self perceived by him’ that a man knows that anexternal object exists. This is the sort of thing one has in mind when one talks of a strongstreak of perceptual realism in Locke, but it has of course been recognized by those who holdthat it cannot be taken at face value. The issue then becomes, I think, whether other thingsLocke says suggest that, really, all we are aware of is mind-dependent items, or whether thedominant thought is simply that, though we are aware of the things, the way they appear to uswill depend in large part on facts about our sensory apparatus. For an analysis of the issuesthat divide commentators here, see Tipton, [3.59].18 Bennet, [3.36], 120.19 Ryle [3.57], 147. The remark, made in conversation with Bertrand Russell, was set in thecontext of a recognition that ‘Locke made a bigger difference to the whole intellectualclimate of mankind than anyone had done since Aristotle’. The paper in which he reports it isthus not dismissive, but rather Ryle’s attempt to explain what Locke’s great contribution was.Press, 1975.3.4 Yolton, J.W. (ed.)An Essay Concerning Human Understanding(abr. edn), London,Dent, 1976.Early Criticisms3.5 Burnet, ThomasRemarks upon an Essay concerning Humane Understanding,London, 1697,Second Remarks(1697), andThird Remarks(1699); ed. G. Watson asRemarks on John Locke,Doncaster, Brynmill Press, 1989.3.6 Carroll, WilliamA Dissertation upon the Tenth Chapter of the Fourth Book of Mr.Locke’s Essay (etc.) ,London, 1706; repr. Bristol, Thoemmes, 1990.3.7 Lee, HenryAnti-Scepticism: Or,Notes upon each Chapter of Mr. Lockeys Essay(etc.),London, 1702; repr. New York, Garland, 1978.3.8 Leibniz, G.W.New Essays on Human Understanding,first pub. 1765, trans. and ed.P.Remnant and J.Bennett, Cambridge, Cambridge University Press, 1981.3.9 Lowde, JamesA Discourse concerning the Nature of Man…, London, 1694; repr.New York, Garland, 1979.3.10 Norris, JohnCursory Reflections upon a Book call’d, an Essay concerning HumanUnderstanding.Appended to hisChristian Blessedness,London, 1690; repr. NewYork, Garland, 1978.3.11 Sergeant, JohnSolid Philosophy Asserted, against the Fancies of the Ideaists,London, 1697; repr. New York, Garland, 1984.3.12 Stillingfleet, EdwardA Discourse in Vindication of the Doctrine of the Trinity,London, 1696.3.13——The Bishop of Worcester’s Answer to Mr. Locke’s Letter, concerning somePassages relating to his Essay (etc.),London, 1697.3.14——The Bishop of Worcester’s Answer to Mr. Locke’s Second Letter…,London,1698.3.15 Yolton, J.W.John Locke and the Way of Ideas,Oxford, Oxford University Press,1956. (A survey of many early responses.)Bibliographies3.16 Christophersen, H.O.A Bibliographical Introduction to the Study of John Locke,Oslo, 1930; repr. New York, Franklin, 1968.3.17 Hall, R. and Woolhouse, R.Eighty Years of Locke Scholarship,Edinburgh,Edinburgh University Press, 1983.3.18The Locke Newsletter,published annually since 1970 by Roland Hall of theDepartment of Philosophy at the University of York, contains a ‘Recent Publications’section.Biographies3.19 Fox Bourne, H.R.The Life of John Locke,London, 1876; repr. Bristol, Thoemmes,1991.3.20 Cranston, M.John Locke: A Biography,London, Longmans, 1957.General Surveys3.21 Ayers, M.R.Locke,2 vols, London, Routledge, 1991.3.22 Aaron, R.I.John Locke,1st edn 1937; 3rd edn, Oxford, Clarendon Press, 1971.3.23 Brandt, R. (ed.)John Locke: Symposium Wolfenbüttel 1979,Berlin, de Gruyter,1981.3.24 Duchesneau, F.L’Empirisme de Locke,The Hague, Nijhoff, 1973.3.25 Gibson, J.Locke’s Theory of Knowledge and its Historical Relations,Cambridge,Cambridge University Press, 1917.3.26 Mabbott, J.D.John Locke,London, Macmillan, 1973.3.27 Mackie, J.L.Problems from Locke,Oxford, Clarendon Press, 1976.3.28 O’Connor, D.J.John Locke,New York, Dover, 1967.3.29 Squadrito, K.Locke’s Theory of Sensitive Knowledge,Washington, University Pressof America, 1978.3.30 Tipton, I.C. (ed.)Locke on Human Understanding: Selected Essays,Oxford, OxfordUniversity Press, 1977.3.31 Webb, T.E.The Intellectualism of Locke,Dublin, 1857; repr. Bristol, Thoemmes,1990.3.32 Woolhouse, R.S.Locke’s Philosophy of Science and Knowledge,Oxford, Blackwell,1971.3.33——Locke,Brighton, Harvester, 1983.3.34 Yolton, J.W.Locke and the Compass of Human Understanding,Cambridge,Cambridge University Press, 1970.Comparative Studies and Special Themes3.35 Alexander, P.Ideas, Qualities and Corpuscles: Locke and Boyle on the ExternalWorld,Cambridge, Cambridge University Press, 1985.3.36 Bennett, J.Locke, Berkeley, Hume: Central Themes,Oxford, Clarendon Press, 1971.3.37 Jolley, N.Leibniz and Locke: A Study of the New Essays on Human Understanding,Oxford, Clarendon Press, 1984.3.38 Schouls, P.A.The Imposition of Method: A Study of Descartes and Locke,Oxford,Clarendon Press, 1980.3.39 Yolton, J.W.Perceptual Acquaintance from Descartes to Reid,Oxford, Blackwell,1984.3.40——Thinking Matter: Materialism in Eighteenth-Century Britain,Oxford,Blackwell, 1984.3.41——Locke and French Materialism,Oxford, Clarendon Press, 1991.Articles and Chapters3.42 Ashworth, E.J. ‘Locke on Language’,Canadian Journal of Philosophy14 (1984):45–73.3.43 Ayers, M.R. ‘The Ideas of Power and Substance in Locke’s Philosophy’, first pub.1975, repr. in [3.30], above.3.44 Ayers, M.R. ‘Locke’s Logical Atomism’, inRationalism, Empiricism and Idealism,ed. A.Kenny, Oxford, Clarendon Press, 1986.3.45 Barnes, J. ‘Mr. Locke’s Darling Notion’,Philosophical Quarterly22 (1972): 193–214.3.46 Bennett, J. ‘Substratum’,History of Philosophy Quarterly4 (1987): 197–215.3.47 Buchdahl, G. ‘Locke: Narrowing the Limits of Scientific Knowledge’, ch. 4 in hisMetaphysics and the Philosophy of Science,Oxford, Blackwell, 1969.3.48 Curley, E.M. ‘Locke, Boyle, and the Distinction between Primary and SecondaryQualities’,Philosophical Review81 (1972): 438–64.3.49 Flew, A. ‘Locke and the Problem of Personal Identity’,Philosophy26 (1951): 53–68.3.50 Harris, J. ‘Leibniz and Locke on Innate Ideas’, first pub. 1974, repr. in [3.30], above.3.51 Kretzmann, N. The Main Thesis of Locke ‘s Semantic Theory’, first pub. 1968, repr.in [3.30], above.3.52 Kroll, R.W.F. ‘The Question of Locke’s Relation to Gassendi’,Journal of theHistory of Ideas45 (1984): 339–59.3.53 Jackson, R. ‘Locke’s Distinction between Primary and Secondary Qualities’,Mind38 (1929): 56–76.3.54 Laudan, L. ‘The Nature and Sources of Locke’s Views on Hypotheses’, first pub.1967, repr. in [3.30], above.3.55 Mandelbaum, M. ‘Locke’s Realism’, Essay 1 in hisPhilosophy, Science and SensePerception,Baltimore, John Hopkins Press, 1964.3.56 Michael, F.S. and E. ‘The Theory of Ideas in Gassendi and Locke’,Journal of theHistory of Ideas51 (1990): 379–99.3.57 Ryle, G. ‘John Locke’, first pub. 1967, repr. in hisCollected Papers,vol. 1, London,Hutchinson, 1971.3.58 Stewart, M.A. ‘Locke’s Mental Atomism and the Classification of Ideas’ (in twoparts),The Locke Newsletter10 (1979): 53–82, and 11 (1980): 25–62.3.59 Tipton, I.C. ‘ “Ideas” and ”Objects“: Locke on Perceiving ”Things” ’, inMinds,Ideas, and Objects: Essays on the Theory of Representation in Modern Philosophy,ed.P.D.Cummins and G.Zoeller, Atascadero, Calif., Ridgeview Publishing Company,1992.3.60 Wilson, M.D. ‘Superadded Properties: The Limits of Mechanism in Locke’,American Philosophical Quarterly16 (1979): 143–50.3.61 Winkler, K.P. ‘Locke on Personal Identity’,Journal of the History of Philosophy29(1991): 201–26.