J.S.MillLogic and metaphysicsJohn SkorupskiENLIGHTENMENT AND ROMANTICISM IN MILL’S PHILOSOPHYMill’s importance as one of the major figures of nineteenth-century politics and culture,and the current interest in him as a moral and political philosopher, are both so great thatthey make it hard to see him in another aspect—as a leading contributor to the Britishtradition of epistemology and metaphysics. Yet it was theSystem of Logic(1843) thatfirst established his reputation; and his views in this field remain as interesting andrelevant as his better known views in ethics and politics.Throughout his intellectual life Mill sought to weave together the insights ofenlightenment and Romanticism. He applied Romantic idealism’s moral understanding toutilitarianism’s concepts of character, imagination and purpose, freedom and reason,human good. To German Romanticism he owes one of his master themes—that of theculture of human nature as a whole, both in its diverse spontaneity and in its rationalautonomy. But the metaphysical and psychological foundations of his thought liesecurely in the naturalistic empiricism of the British school—and, moreover, in its radicaland associationist, rather than its conservative and innatist, wing. Thus the deepestquestions about Mill’s philosophical success turn on the possibility of such a synthesis,and on how far he achieved it.Reasons for doubt centre on two great issues, which at bottom are linked. Must notnaturalism subvert reason, as Kant thought? And must not a natural science of man—ascientific psychology—subvert the understanding from within, themoralpsychology ofautonomy and expressive spontaneity, which Mill shares with the ‘Germano-Coleridgeans’(as he called them)? Both questions lead us to theSystem of Logic,the first to itsanalysis of deductive and inductive reasoning, the second to its treatment of freedom anddeterminism.They remain important issues in contemporary philosophy. Beyond thesetwo questions about the coherence of Mill’s thought, there is a third—whether hisassociationist psychology can be reconciled with the idea of determinate humanpotentiality he requires for his account of ‘man as a progressive being’. But this questiondoes not have the direct contemporary significance that the other two have and will notbe discussed here.NATURALISM AND SCEPTICISMNaturalism is the view that the mind is an entirely natural entity—a part of the naturalorder. But if the mind is only a part of nature, it seems that no real knowledge of thenatural world can bea priori. Either all real knowledge isa posteriori,grounded inexperience, or there is no real knowledge. That this consequence genuinely follows fromnaturalism Mill and Kant would have agreed. The difference between them was that Mill,unlike Kant, thought that knowledge could be grounded on such a basis. Thus the purposeof theSystem of Logicwas, firstly, to spell out the full extent of epistemologicalempiricism—that is, of the view that all knowledge isa posteriori—and, secondly, toshow how knowledge is possible on that basis. Its greatest achievement is the radicalismand the rigour with which it presses through to the first of these objectives.Before we examine theSystemit will be useful to draw some further broad contrastsbetween Mill, Kant, David Hume and Thomas Reid. Unlike Hume, Kant or even Reid,Mill shows no interest at all in scepticism. He agrees with Kant that naturalism mustremovea priorigrounding from the common-sense principles which Reid presents. Hedoes not agree with Reid that those principles are ‘innate’, but he also sees—though withless clarity, as we shall see—that even if they were, that would not give them anepistemological, as against a merely psychological, independence of experience. Yet hedoes not unleash a sceptical attack on reason as Hume does, nor does he see any need todefend reason against such an attack. In fact he sees no crisis of reason, and it is this thatsets him apart most fundamentally from the Critical legacy of Kant.Here he is loyal to his Benthamite inheritance. The Benthamites wished to distancethemselves from Hume’s scepticism just as firmly as the Scottish common-sensists did—unlike the latter, though, they felt no call to respond systematically to it. Mill agreed withthem: in this respect his attitude was English rather than Scottish. More broadly,however, both Mill and Reid belong in that British naturalistic camp which believes thatno serious philosophical lesson can be drawn from scepticism. For neither of themthinks—as Hume did—that sceptical arguments are sound and significant, that they showsomething of negative importance about reason. The difference between them is ratherthat Reid believes that scepticism stems solely from an erroneous theory of mind, and canbe entirely defused by denying the existence of the objects postulated by that theory—ideas—while Mill in contrast never engages with scepticism at all.If one thinks that scepticism is both unanswerable and unserious this may be the truephilosophic wisdom. Whether it is wisdom or evasion is a question which keeps onreturning in philosophy. But whatever view one takes on it one will misunderstand theSystem of Logicif one does not grasp that it is a work of what a contemporaryphilosopher in the same tradition, W.V.O.Quine, has called ‘naturalized epistemology’.One of the ways in which it is, is precisely this: that it neither raises nor seeks to answersceptical questions.THE ANALYSIS OF LANGUAGE: LOGIC AND MATHEMATICS CONTAIN REAL INFERENCESFundamental to theSystemis a distinction Mill draws between ‘verbal’ and ‘real’propositions, and correspondingly, between ‘merely apparent’ and ‘real’ inferences. Heapplies it with greater strictness, and addresses his thesis, that merely apparent inferenceshave no genuine cognitive content, with greater resolution, than anyone had done before.We can best reconstruct it by starting with the notion of a merely apparent inference.An inference is merely apparent when no real inferential move has been made. For this tobe so, the conclusion must literally have been asserted in the premisses. In such a case,there can be no epistemological problem about justifying the apparent inference—thereisnothing to justify. A verbal proposition can now be defined as a conditional propositioncorresponding to a merely apparent inference. (This is not the whole of Mill’s distinction,for he also counts elementary inferences and propositions concerning identity as verbal;but we can ignore that for the moment.)The distinction corresponds, as Mill himself notes, to that which Kant makes between‘analytic’ and ‘synthetic’. (Kant formulates it for affirmative predicative propositions,and so does Mill, but the version given in the previous paragraph can be used to avoidthis limitation.) But there is also a broader notion of analyticity, which has beeninfluential in this century and which may also be thought to be implicit in some, thoughnot all, of Kant’s formulations. It defines an analytic truth as one from whose negation acontradiction can be deduced, with the help, where necessary, of definitionaltransformations, and using principles of logic alone. In the broad sense of ‘analytic’, itbecomes a trivial truth that logical principles are analytic. But what is then no longertrivial is the crucial thesis that analytic propositions have no genuine cognitive content,and hence pose no epistemological problem.If we keep to Mill’s understanding of the distinction between ‘verbal’ and ‘real’, whichcorresponds to the narrower Kantian notion of analyticity, pure mathematics, and logicitself, contain ‘real’ propositions and inferences with genuine cognitive content. The clearrecognition of this fact is the chief philosophical achievement of theSystem of Logic. Forif Mill is also right in holding that naturalism entails that no real proposition isa priori,then he has shown the implications of naturalism to be radical indeed. Not onlymathematics but logic itself will be empirical.To demonstrate that logic and mathematics contain real propositions Mill has toembark on an extensive semantic analysis of sentences and terms (he calls them ‘names’),of syllogistic logic, and of the so-called ‘Laws of Thought’. His analysis has manyimperfections and he never unifies it in a fully general account. But he does supply thefoundations of such an account, and in doing so takes the empiricist epistemology oflogic and mathematics to a wholly new level.The starting point is a distinction between the denotation and connotation of names.Names, which may be general or singular, denote objects and connote attributes ofobjects. (Attributes may themselves be denoted by ‘abstract’ names, though the term ismisleading, for Mill conceives attributes nominalistically). A general name connotesattributes and denotes each object which has those attributes. Most singular names alsoconnote attributes, but their grammatical construction indicates that they denote just oneobject if they denote at all.There is however an important class of singular names—‘proper names’ in theordinary sense, such as ‘Dartmouth’—which denote an object without connoting anyproperty. Identity propositions which contain only such non-connotative names, as ‘Tullyis Cicero’, are in Mill’s view verbal. They lack content in the sense that, according toMill, the only information conveyed is about the names themselves: ‘Tully’ denotes thesame object as ‘Cicero’ does. Mill’s point is that there is no fact in the world to which‘Cicero is Tully’ corresponds; a thought similar to that which inspired Wittgenstein’streatment of identity in theTractatus. The obvious difficulty about assimilating them toverbal propositions on this basis is that knowledge that Cicero is Tully is nota priori. Wecannot know the proposition to be true just by reflecting on the meaning of the names—whereas Mill’s overall inten-tion is that the class of verbal propositions should beidentical with the class of propositions which are innocuouslya, priori becauseempty ofcontent. He does not seem to notice this difficulty.The meaning of a declarative sentence—‘the import of a proposition’—is determinedby the connotation, not the denotation, of its constituent names; the sole exception beingconnotationless proper names, where meaning is determined by denotation. (Again thereis something puzzling here, for it needs to be explained how this thesis about the meaningof proper names is to be reconciled with the aposteriority of ‘Cicero is Tully’.) Millproceeds to show how the various syntactic forms identified by syllogistic theory yieldconditions of truth for sentences of those forms, when the connotation of their constituentnames is given.Armed with this analysis he argues that logic contains real inferences and propositions.(He assumes that to assert a conjunction,A and B,is simply to assertAand to assertB.He definesA or Bas ‘If notA,thenB,and if notB,thenA’. ‘IfAthenB’ means, hethinks, ‘The propositionBis a legitimate inference from the propositionA’.)His strategy is an admirably forceful pincer movement. One pincer is an indirectargument. If logic did not contain real inferences, all deductive reasoning would be apetitio principii,a begging of the question—it could produce no new knowledge. Yetclearly it does produce new knowledge. So logic must contain real inferences. The otherpincer is a direct semantic analysis of the supposed ‘axioms’ of syllogistic reasoning andof the laws of thought. It shows them to be real and not merely verbal.The execution of this strategy is flawed, because Mill mixes it up with an interestingbut distinct objective. He wants to show that ‘all inference is from particulars toparticulars’. The point is to demystify the role general propositions play in thought. Heargues that in principle they add nothing to the force of an argument; particularconclusions could always be derived inductively direct from particular premisses. Theirvalue is psychological. They play the role of ‘memoranda’, summary records of theinductive potential of all that we have observed, and they facilitate ‘trains ofreasoning’ (as e.g. in ‘This isA,allAs areBs, noBs areCs, so this is notC’).Psychologically they greatly increase our memory and reasoning power, butepistemologically they are dispensable.As Mill presents it, this thesis is tied in with his rejection of ‘intuitive’ knowledge ofgeneral truths and with his inductivism (which we shall come to shortly). For it assumesthe illegitimacy ofhypothesizinggeneral propositions, as against generalizing to themfrom observation of singular conjunctions. Beneath this, however, there lies a deeper andobscurer sense in which a radical empiricist must hold that all inference is fromparticulars to particulars. For consider the inference from ‘Everything isF’ to ‘aisF’. Isit a real or merely apparent inference? It is impossible to hold it real if one also wishes toargue that real inferences area, posteriori. But the only way of treating it as verbal whichis open to Mill is to treat the premiss as a conjunction: ‘aisFandbisFand…’ If thatapproach is precluded then all that remains is to deny that ‘Everything isF’ isprepositional—it must, rather, express an inferential commitment.Both approaches are very close to the surface in Mill’s discussion of the syllogism, andhe comes closest to the latter when he emphasizes that a general proposition is ‘amemorandum of the nature of the conclusions which we are prepared to prove’. But theseissues about generality (and about conditional propositions) do not emerge clearly in hisanalysis; like his treatment of proper names and of identity, they were destined to make adecisive appearance on the agenda of philosophical logic only later, in the twentiethcentury.MILL’S EMPIRICIST VIEW OF LOGIC, GEOMETRY AND ARITHMETICThough Mill’s treatment of generality and the syllogism is somewhat confused andopaque, he is quite clear cut in holding the laws of contradiction and excluded middle tobe real—and thereforea posteriori—propositions. He takes it that ‘notP’ is equivalent inmeaning to ‘it is false thatP’; if we further assume the equivalence in meaning ofPand‘It is true that P’, the principle of contradiction becomes, as he puts it, ‘the sameproposition cannot at the same time be false and true’. ‘I cannot look upon this’ he says‘as a merely verbal proposition. I consider it to be, like other axioms, one of our first andmost familiar generalizations from experience.’ He makes analogous remarks aboutexcluded middle, which turns—on these definitions—into the principle of bivalence,‘Either it is true thatPor it is false thatP’.A truly radical empiricism! After this it is not surprising to find the same broadstrategy applied to mathematics. If it was merely verbal, mathematical reasoning wouldbe apetitio principii. Moreover a detailed semantic analysis shows that it does containreal propositions.Mill provides brief but insightful empiricist sketches of geometry and arithmetic. Ongeometry he is particularly good. The theorems of geometry are deduced from premisseswhich are real propositions inductively established. (Deduction is itself of course aprocess of real inference.) These premisses, where they are not straightforwardly true ofphysical space, are true in the limit. Geometrical objects—points, lines, planes—are idealor ‘fictional’ limits of ideally constructible material entities. Thus the real empiricalassertion underlying an axiom such as ‘Two straight lines cannot enclose a space’ issomething like ‘The more closely two lines approach absolute breadthlessness andstraightness, the smaller the space they enclose’.Mill applies his distinction between denotation and connotation to show thatarithmetical identities such as ‘Two plus one equals three’ are real propositions. Numberterms denote ‘aggregates’ and connote certain attributes of aggregates. (He does not saythat they denote those attributes of the aggregates, though perhaps he should have done.)‘Aggregates’ are natural not abstract entities—‘collections’ or ‘agglomerations’individuated by a principle of aggregation. This theory escapes some of the famous butrather unfair criticisms Frege later made of it, but its viability none the less remainsextremely doubtful. The trouble is that the respects in which aggregates have to differfromsetsif they are to be credibly natural, and not abstract, entities are precisely those inwhich they seem to fail to produce a fully adequate ontology for arithmetic. (One can forexample number numbers, but can there be aggregates of aggregates, or of attributes ofaggregates, if aggregates are natural entities?)However this may be, Mill’s philosophical programme is clear. Arithmetic, like logicand geometry, is a natural science, concerning a particular department of the laws ofnature—those concerning the compositional properties of aggregates. The upshot is thatthe fundamental principles of arithmetic and geometry, as well as of logic itself, are real.Given epistemological empiricism, it follows that deductive reasoning, ‘ratiocination’, isempirical. Mill has provided the first thoroughly naturalistic analysis of meaning and ofdeductive reasoning itself.He distinguishes his own view from three others—‘conceptualism’, ‘nominalism’ and‘realism’.‘Conceptualism’ is his name for the view which takes the objects studied by logic to bepsychological states or acts. It holds that names stand for ‘ideas’ which make upjudgements and that ‘a proposition is the expression of a relation between two ideas’. Itconfuses logic and psychology by assimilating propositions to judgements and attributesof objects to ideas. Against this doctrine Mill insists thatAll language recognises a difference between a doctrine or opinion, and the factof entertaining the opinion; between assent, and what is assented to… Logic,according to the conception here formed of it, has no concern with the nature ofthe act of judging or believing; the consideration of that act, as a phenomenon ofthe mind, belongs to another science.(7:87)He traces conceptualism to the seventeenth century: it was introduced by Descartes,fostered by Leibniz and Locke, and has obscured the true status of logic—which issimply ‘the Science of Science’—ever since.The nominalists—Mill cites Hobbes—hold that logic and mathematics are entirelyverbal. Mill takes this position much more seriously than conceptualism and seeks torefute it in detail. His main point is that nominalists are able to maintain their view onlybecause they fail to distinguish between the denotation and the connotation of names,‘seeking for their meaning exclusively in what they denote’ (7:91).Nominalists and conceptualists both hold that logic and mathematic can be known nonempirically,while yet retaining the view that no real proposition about the mindindependentworld can be so known—but both are confused. But what if one abandonsthe thesis that no real proposition about the mind-independent world can be knownaThe nineteenth century 86priori? The realists do that—they hold that logical and mathematical knowledge isknowledge of universals existing in an abstract Platonic domain; the terms that make upsentences being signs that stand for such universals. This is the view Mill takes leastseriously—but versions of it were destined to stage a major revival in philosophy, andsemantic analysis would be their main source.In fact in the contemporary use of the term, Mill is himself a nominalist—he rejectsabstract entities. That is why he treats aggregates as concrete objects, and attributes asnatural properties rather than universals. But, just as severe difficulties lie in the way oftreating the ontology of arithmetic in terms of aggregates rather than classes, so there aresevere difficulties in the way of treating the ontology of general semantics withoutappealing to universals and classes, as well as to natural properties and objects. We canhave no clear view of how Mill would have responded to these difficulties had they beenmade evident to him. But we can I think be fairly sure that he would have sought tomaintain his nominalism.However, the central target of Mill’s attack is the doctrine that there are reala prioripropositions. What, he asks, in practice goes on, when we hold a real proposition to betruea priori? We find its negation inconceivable, or that it is derived, by principleswhose unsoundness we find inconceivable, from premisses whose negation we findinconceivable. Mill is not offering a definition of what is meant by such terms as‘apriori’,or ‘self-evident’; his point is that facts about what we find inconceivable are allthat lends colour to the use of these terms.They are facts about the limits, felt by us from the inside, on what we can imagineperceiving. Mill thought he could explain these facts about unthinkability, or imaginativeunrepresentability, in associationist terms, and spent many pages claiming to do so. Theyare not very convincing pages, but that does not affect his essential point, which is this:the step from our inability to represent to ourselves the negation of a proposition, toacceptance of its truth, calls for justification. Moreover, the justificationitselfmust bea,prioriif it is to show that the proposition is knowna, priori.(Thus Mill is prepared forexample to concede the reliability of geometrical intuition: but he stresses that itsreliability is an empirical fact, itself known inductively.)At this point, Kant could agree. To vindicate the possibility of synthetica prioriknowledge calls, he claims, for nothing less than transcendental idealism. But withoutsynthetica prioriknowledge, knowledge as such becomes impossible. The verypossibility of knowledge requires that there bea priorielements in our knowledge.THE METHODS OF INDUCTION AND THEIR STATUSTheSystem of Logicin contrast sets out to vindicate in general terms the possibility of ascheme of scientific knowledge which appeals at no point whatever to ana prioriprinciple. One point in the opposition betweenCriticalandnaturalisticepistemology, aswe have noticed, is the latter’s refusal to take seriously pure sceptical arguments; butnaturalistic epistemology also has two other ingredients—an appeal to a natural, or inMill’s word ‘spontaneous’, agreement in propensities to reason, and what may be calledan ‘internal’ vindication of these fundamental reasoning propensities. All threeingredients are present in theSystem of Logic.For Mill, the basic form of reasoning—epistemologically, historically andpsychologically—is enumerative induction, simple generalization from experience. Thisis the diposition to infer to the conclusion that allAs areBfrom observation of a numberofAs which are allB. (Or to the conclusion that a given percentage of allAs areBfromobservation of that percentage ofBs among a number ofAs.) We spontaneously agree inreasoning that way, and in holding that way of reasoning to be sound. The proposition‘Enumerative induction is rational’ is not a verbal proposition. But nor is it grounded inana prioriintuition. All that Mill will say for it is that people in general, and the readerin particular, in fact agree on reflection in accepting it. It is on that basis alone that herests its claim.Mill’s problem of induction, the problemhewants to solve, is not Hume’s. Insidestepping the purely sceptical question about induction, Mill uses the analogy of atelescope which Thomas Reid had also used in a similar context—though in Reid thetelescope is Reason as against Common Sense, while in Mill it is Scientific as againstspontaneous induction:Assuredly, if induction by simple enumeration were an invalid process, noprocess grounded on it would be valid; just as no reliance could be placed ontelescopes, if we could not trust our eyes. But though a valid process, it is afallible one, and fallible in very different degrees: if therefore we can substitutefor the more fallible forms of the process, an operation grounded on the sameprocess in a less fallible form, we shall have effected a very materialimprovement. And this is what scientific induction does.(7:567–8)Mill’s aim is to provide the telescope. The problem he starts from is not a sceptical but aninternal one—why is it that some inductions are more trustworthy than others?Why is a single instance, in some cases, sufficient for a complete induction,while in others, myriads of concurring instances, without a single exceptionknown or presumed, go such a very little way towards establishing a universalproposition? Whoever can answer this question…has solved the problem ofinduction.(7:314)Mill’s answer takes the form of a natural history of the ‘inductive process’. The point isto show how that process is internally vindicated by its actual success in establishingregularities, and how it eventually gives rise to more searching methods of investigation.Mankind begins with ‘spontaneous’ and ‘unscientific’ inductions about particularunconnected natural phenomena or aspects of experience. Generalizations accumulate,interweave and are found to stand the test of time: they are not disconfirmed by furtherexperience. As they accumulate and interweave, they justify the second-order inductiveconclusion thatallphenomena are subject to uniformity, and, more specifically, that allhave discoverable sufficient conditions. In this less vague form, the principle of generaluniformity becomes, given Mill’s analysis of causation, the Law of Universal Causation.This conclusion in turn provides (Mill believes) the grounding assumption for a new styleof reasoning about nature—eliminative induction.In this type of reasoning, the assumption that a type of phenomenon has uniformcauses, together with a (revisable) assumption about what its possible causes are, initiatesa comparative inquiry in which the actual cause is identified by elimination. Millformulates the logic of this eliminative reasoning in his well-known ‘Methods ofEmpirical Inquiry’. His exposition is rather garbled but he was right to be proud of it, forit did show how effective eliminative reasoning can be. His picture of the interplaybetween enumerative and eliminative reasoning, and of the way it entrenches, fromwithin, our rational confidence in the inductive process, is elegant and penetrating.The improved scientific induction which results from this new style of reasoning spillsback on to the principle of Universal Causation on which it rests, and raises its certaintyto a new level. That in turn raises our confidence in the totality of particular enumerativeinductions from which the principle is derived. In short, the amount of confidence withwhich one can rely on the ‘inductive process’ as a whole depends on the point which hasbeen reached in its natural history—though the confidence to be attached to particularinductions always remains variable.The fundamental norm of scientific reasoning, enumerative induction, is not a merelyverbal principle. But what can it mean to deny that it isa priori? Mill says that we learn‘the laws of our rational faculty, like those of every other natural agency’, only by ‘seeingthe agent at work’. He is quite right: we can find out what our most basic reasoningdispositions are, only by critical reflection on our practice. This reflective scrutiny ofpractice is, in acertainsense, ana posterioriprocess. It examines dispositions which wehave before we examine them. Having examined our dispositions, we reach a reflectiveequilibrium in which we endorse some—and perhaps reject others. We endorse them assound norms of reasoning.But at this point the sceptic will ask by what right we do so—and Mill rules hisquestion out of order. So denying that the fundamental principle of induction isa prioricomes down, it seems, to just that ruling. Might it not just as well have been said that theprinciple isa priori? But that would suggest that there was some further story, Platonic ortranscendental, to be had, which explained and legitimated our reasoning practice, andthisis what Mill denies.So too does the sceptic: the fact that the sceptic and the naturalist agree on that hardlyshows why it is all right to rule the sceptic’s question out of order. It seemed obvious toMill’s epistemological critics, whether they were realists or post-Kantian idealists, thatthis was evasive: naturalism could seem to differ from scepticism only by beinguncritical.Where Hume launches a sceptical assault on reason, Mill opens upallour beliefs to anempirical audit. Hume takes deduction for granted and raises sceptical questions aboutinduction. Mill takes the legitimacy of natural reasoning propensities for granted, but hequestions the aprioricity of deduction. Hume and Mill are both naturalistic radicals—butin quite different ways. Mill leaves no real principle of deduction, no common-sensebelief entrenched—with one telling exception. The exception is our disposition to rely onthe deliverances of memory, which he acknowledges, in the manner of Thomas Reid, tobe ‘ultimate’. But, with this exception, the only ultimate principle that survives in Mill’sscience of science is enumerative induction. The whole of science, he thinks, can be builtby this single instrument.HYPOTHESISThis is Mill’sinductivism—the view that enumerative induction is the onlyultimatemethod of inference which puts us in possession of new truths. Is he right in thinking it tobe so? The question produced an important, if confused, controversy between him andWilliam Whewell (1794–1866). Their disagreement concerned the role of hypotheses.Whewell argued that the Hypothetical Method was fundamental in scientific inquiry: themethod in which one argues to the truth of an hypothesis from the fact that it wouldexplain observed phenomena.Mill had read Whewell’sHistory of the Inductive Sciences(1837), and he could hardlyfail to be aware of the pervasiveness of hypotheses in the actual process of inquiry, or oftheir indispensableness in supplying working assumptions—their ‘heuristic’ value,Whewell called it. The same point—the indispensableness of hypotheses in providinglines of inquiry—had been emphasized by the Frenchman Auguste Comte, with whoseCours de philosophie positive(which began to appear in 1830) Mill was also familiar.But what Mill could not accept was that the mere fact that an hypothesis accounted forthe datain itselfprovided a reason for thinking it true. He denied that the HypotheticalMethod constituted, in its own right, a method of arriving at new truths from experience.Yet Whewell’s appeal was to the actual practice of scientific reasoning, as observed inthe history of science. An appeal of that kind was precisely what Mill, on his ownnaturalistic principles, could not ignore. The disposition to hypothesize is spontaneous, sowhy should it not be recognized as a fundamental method of reasoning to truth, asenumerative induction is?Mill’s refusal to recognize it is not arbitrary. The essential point underlying it is apowerful one: it is the possibility that a body of data may be explained equally well bymore than one hypothesis. What justifies us in concluding, from the fact that a particularstory would, if true, explain the data, that it is a true story? Other stories may equallyexplain the data.Mill places great emphasis on the increasingly deductive and math-ematicalorganization of science—that is quite compatible with his inductivism, and indeed centralto it. But he takes the ‘Deductive Method’ of science to involve three steps: ‘induction’,‘ratiocination’, and ‘verification’. A paradigm, in his view, is Newton’s explanation ofKepler’s laws of planetary motion. Induction establishes causal laws of motion andattraction, ratiocination deduces lower level regularities from them in conjunction withobserved conditions, and verification tests these deduced propositions againstobservation. (Though this was not, and did not need to be, the historical order of inquiry.)Butthe Hypothetical Method suppresses the first of the three steps, the induction toascertain the law; and contents itself with the other two operations, ratiocinationand verification; the law which is reasoned from being assumed, instead ofproved.(7:492)Mill agrees that it is legitimate to do this when the hypothesis in question has effectivelybeen shown, by eliminative reasoning, to be the only one consistent with the facts. Heallows various other cases of apparently purely hypothetical reasoning which are, in hisview, genuinely inductive.When all such cases have been taken into account, we are left with pure cases of theHypothetical Method, in which the causes postulated are not directly observable, and notsimply because they are assumed to operate—in accordance with known laws, inductivelyestablished—in regions of time or space too distant to observe. What are we to say ofsuch hypotheses? For example of the ‘emission’ theory, or the ‘undulatory’ theory oflight? They cannot be accepted as inductively established truths, not even as probableones:an hypothesis of this kind is not to be received as probably true because itaccounts for all the known phenomena; since this is a condition sometimesfulfilled tolerably well by two conflicting hypotheses; while there are probablymany others which are equally possible, but which from want of anythinganalogous in our experience, our minds are unfitted to conceive.(7:500)Such an hypothesis can suggest fruitful analogies, Mill thinks, but cannot be regarded asyielding a new truth itself. The data do not determine a unique hypothesis: it is thispossibility, of underdetermination, which stops him from accepting hypotheticalreasoning as an independent method of achieving truth, even though it is a mode ofreasoning as spontaneous as enumerative induction.In seeing the difficulty Mill is certainly on sound ground. What he does not see,however, is how much must be torn from the fabric of our belief if inductivism is appliedstrictly. Thus, for example, while his case for empiricism about logic and mathematics isvery strong, it is his methodology of science which then forces him to hold that we knowbasic logical and mathematical principles only by an enumerative induction. And that isdesperately implausible.So it is an important question whether the difficulty can be resolved—and whether itcan be resolved within a naturalistic framework, which does not yield to idealism. Ifnaturalism can endorse the hypothetical method, it can develop a more plausibleempiricism about logic and mathematics than Mill’s. But the ramifications of hisinductivism are even wider, as becomes apparent if we turn to his general metaphysics.THE DOCTRINE OF THE RELATIVITY OF KNOWLEDGEMill sets this out in hisExamination of Sir William Hamilton’s Philosophy(1865). SirWilliam Hamilton (1791–1856) was a Scotsman who sought to moderate the views ofReid and Kant. He was a philosopher of subtlety and erudition (or even pedantry), the lasteminent representative of the school of Scottish common sense, and a ferociouscontroversialist. Mill deemed him a pillar of the right-thinking intellectual establishment,ripe for demolition. But by the time theExaminationappeared Hamilton’s death hadmade it impossible for him to reply—a fact which predictably caused Mill some regret.For the present-day reader, however, what is more regrettable is that Mill’s discussion ofgeneral metaphysical issues should be cast in so polemical a form. It means thatimportant issues, particularly on the nature of logic and thought, remain shrouded inobscurity. Mill does however give himself space to develop his view of our knowledge ofthe external world.He begins by expounding a doctrine which he rightly takes to be generally accepted (inhis time) on all sides. It affirmsthat all the attributes which we ascribe to objects, consist in their having thepower of exciting one or another variety of sensation in our minds; that anobject is to us nothing else than that which affects our senses in a certainmanner; that even an imaginary object is but a conception, such as we are ableto form, of something which would affect our senses in some new way; so thatour knowledge of objects; and even our fancies about objects, consist of nothingbut the sensations which they excite, or which we imagine them exciting, inourselves.(9:6)This is ‘the doctrine of the Relativity of Knowledge to the knowing mind’. But there aretwo forms in which it may be held.According to one of the forms, the sensations which, in common parlance, weare said to receive from objects, are not only all that we can possibly know ofthe objects, but are all that we have any ground for believing to exist. What weterm an object is but a complex conception made up by the laws of association,out of the ideas of various sensations which we are accustomed to receivesimultaneously. There is nothing real in the process but these sensations.(9:6)According to the other,there is a real universe of ‘Things in Themselves,’ and… whenever there is animpression on our senses, there is a ‘Thing in itself,’ which is behind thephaenomenon, and is the cause of it. But as to what this Thingis‘in itself,’ we,having no organs except our senses for communicating with it, can only knowwhat our senses tell us; and as they tell us nothing but the impression which thething makes uponus,we do not know what it isin itselfat all. We suppose (atleast these philosophers suppose) that it must be something ‘in itself, but all thatwe know it to be is merely relative to us, consisting in the power of affecting usin certain ways.(9:7)The first form (omitting from it the appeal to laws of association) corresponds to what ismeant by ‘phenomenalism’ as the term is often used by philosophers today—though itwas not so used in Mill’s time.Reid’s point, that sensations are not representative mental images but states of mind,does not contradict the doctrine of the Relativity of Knowledge, any more than his thesisthat we perceive physical objects does. For on his account sensations, states of sensoryconsciousness, do mediate between the objects that excite them and the beliefs aboutthose objects which are prompted by them—they are themselves distinct from both theobjects and the beliefs. I cannot perceive without sensing. But I can sense withoutperceiving. For example I may have a visual sensation which prompts me to believe that Iam seeing a red triangle on a green field. It is then apparently true to say, in an obviousand legitimate sense, that what I am immediately aware or conscious of is my visualsensation. That remains true even if I am perceiving no red triangle because no redtriangle exists. Or, if one objects to talk of consciousnessofa state of consciousness, onemay simply say that my immediate visual consciousness is of a red triangle on a greenfield—in a sense in which that can be true though there is no such triangle.This is already enough to make epistemology, in Mill’s phrase, the ‘Interpretation ofConsciousness’. The very fact of consciousness seems to impose the doctrine of theRelativity of Knowledge. To escape it, something more counter-intuitive would berequired than the sensible points Reid makes about perception and sensation. It isnotoriously difficult to pin down what that might be. Perhaps what is needed is nothingless than a denial that sensation is a category ontologically distinct from that of judgementand dispositions to judge: there is no irreducible category of Pure Experience. But Mill, atany rate, questions the irreducible status of sensation no more than Reid did. And hethinks it must follow that—whether or not weactuallymake an inductive inference fromsensations to objects beyond sensation—such an inference is, epistemologically speaking,required.Is this too hasty? Is it dogmatism on Reid’s part simply to point out that we do formparticular beliefs prompted by particular sensations, beliefs which we just do regard asrational? Cannot these specific cognitive dispositions be defended naturalistically, if thegeneral disposition to make enumerative inductions can? But there is a difference. If weare immediately conscious only of states of affairs of one kind (our own sensory states)and on that basis form beliefs about states of affairs of aquite distinctkind (states ofexternal physical objects) then some warrant is required. Reid needs to show why such awarrant does not have to rely on inductive inference—even though it licenses a belief in astate of affairs on the basis of immediate consciousness of aquite distinctstate of affairs.He must call on warrants which are neither deductive nor inductive. And this requiressupport from ideas in the theory of meaning which had not yet been formed. We shallreturn to the point.MATTER AND MINDMill sets about the notion of an ‘external’ object in great style:What is it we mean, or what is it which leads us to say, that the objects weperceive are external to us, and not a part of our own thoughts? We mean, thatthere is concerned in our perceptions something which exists when we are notthinking of it; which existed before we had ever thought of it, and would exist ifwe were annihilated; and further, that there exist things which we never saw,touched, or otherwise perceived, and things which have never been perceived byman. This idea of something which is distinguished from our fleetingimpressions by what, in Kantian language, is called Perdurability; somethingwhich is fixed and the same, while our impressions vary; something whichexists whether we are aware of it or not, and which is always square (or of someother given figure) whether it appears to us square or round—constitutesaltogether our idea of external substance. Whoever can assign an origin to thiscomplex conception, has accounted for what we mean by the belief in matter.(9:178–9)To assign this origin Mill postulatesthat after having had actual sensations, we are capable of forming theconception of Possible sensations; sensations which we are not feeling at thepresent moment, but which we might feel, and should feel if certain conditionswere present, the nature of which conditions we have, in many cases, learnt byexperience.(9:177)These various possibilities are the important thing to me in the world. Mypresent sensations are generally of little importance, and are moreover fugitive:the possibilities, on the contrary, are permanent, which is the character thatmainly distinguishes our idea of Substance or Matter from our notion ofsensation. These possibilities, which are conditional certainties, need a specialname to distinguish them from mere vague possibilities, which experience givesno warrant for reckoning upon. Now, as soon as a distinguishing name is given,though it be only to the same thing regarded in a different aspect, one of themost familiar experiences of our mental nature teaches us, thatthe different name comes to be considered as the name of a different thing.(9:179–80)We may speak ofsensation conditionalsof the form, ‘If such and such sensations were tooccur, then such and such other sensations would occur with a given degree ofprobability’. (It need not always be certainty.) They express Mill’s famous ‘PermanentPossibilities of Sensation’. ‘Permanent’ is slightly misleading, for there is of course achange in the ‘Permanent’ possibilities of sensation whenever there is change in theworld. Mill also uses other terms—‘certified’, ‘guaranteed’.We regularly find that whole clusters of sensation conditionals are true together,whenever some other sensory condition obtains. Thus whenever we experience thatcondition, we are justified in forming all the conditional expectations expressed in thatcluster of conditionals. Moreover, as well as finding simultaneous correlations betweencertified possibilities of sensation, that is, between the truth of any sensation conditionalin a set and the truth of any other in the set, we also find ‘an Order of succession’.Whenever a given cluster of certified possibilities of sensation obtains, then a certainother cluster follows—a certain other set of sensation conditionalsbecomestrue. ‘Henceour ideas of causation, power, activity…become connected, not with sensations, but withgroups of possibilities of sensation’ (9:181).But even if our reflective concept of matter—as the external cause of sensations—canbe explained on psychological principles, it remains open for someone to accept theproposedoriginfor the concept, while also holding that good grounds can be given forthinking it to have instances. He or she will say that a legitimate inference can be madefrom the existence of the Permanent Possibilities and their correlations to the existence ofan external cause of our sensations. It is at just this point that Mill’s inductivism comesin. Such an inference would be a case of hypothetical reasoning, to an explanation ofexperience which transcended all possible data of experience; and that is just what Millrejects: ‘I assume only the tendency, but not the legitimacy of the tendency, to extend allthe laws of our own experience to a sphere beyond our experience’ (9:187). So theconclusion that matter is the permanent possibility of sensation follows from thecombination of the doctrine of the Relativity of Knowledge and inductivism.If matter is the permanent possibility of sensation, what is mind? Mill considers that‘our knowledge of mind, like that of matter, is entirely relative’. Can the mind then alsobe resolved into ‘a series of feelings, with a background of possibilities of feeling’? Hefinds in this view a serious difficulty: to remember or expect a state of consciousness isnot simply to believe that it has existed or will exist; it is to believe thatI myselfhaveexperienced or will experience that state of consciousness.If, therefore, we speak of the Mind as a series of feelings, we are obliged tocomplete the statement by calling it a series of feelings which is aware of itselfas past and future; and we are reduced to the alternative of believing that theMind, or Ego, is something different from any series of feelings, or possibilitiesof them, or of accepting the paradox, that something whichex hypothesiis but aseries of feelings, can be aware of itself as a series.(9:194)Mill is unwilling to accept ‘the common theory of Mind, as a so-called substance’:nevertheless, the self-consciousness involved in memory and expectation drives him to‘ascribe a reality to the Ego—to my own Mind—different from that real existence as aPermanent Possibility, which is the only reality I acknowledge in Matter’ (9:208).If we discount, this conscientious uncertainty about what to say of the self, thetendency of Mill’s analysis is towards the view that all that exist are experiences in atemporal order. Yet he claims, like others before and after him, that this metaphysics isconsistent with common-sense realism about the world. Phenomenalism, he thinks,leaves common sense and science untouched. In particular, minds and experiences arestill properly to be seen as a part of the natural order.But are the experiences referred to, in the phenomenalist’s analysis, the very same asthose referred to in common sense and scientific talk (call this ‘naturalistic’ talk)? If theyare not, then we have yet to be toldwhatthey are. Then suppose they are the same. Innaturalistic talk, we make reference to subjects and their experiences—and also tophysical objects and their properties. Psychology, including Mill’s psychology, seeks toestablish causal correlations among experiences and their physiological antecedents andconsequents.But if phenomenalism is right, only the experiences are real. Mill thinks we are led tothat by the very standards of reasoning recognized in a naturalistic ‘science of science’,or ‘system of logic’. If he is right, then the naturalistic vision of the world, which seesminds as part of a larger causal order, is self-undermining. For if we are led to theconclusion, that only states of consciousness are real,by an application of naturalism’sown standards,then that conclusion has to be understoodon the same levelas thenaturalistic affirmation that states of consciousness are themselves part of a larger causalorder external to them—and therefore as inconsistent with it. Causal relations cannotexist between fictional entities which are mere markers forpossibilitiesof sensation.So either naturalism undermines itself or there is something wrong with Mill’sinductivist analysis of our natural norms of reasoning, or with his endorsement of thedoctrine of the Relativity of Knowledge, or both. It is not our business to diagnose thesituation further here. But it should not be assumed that Mill’s most fundamental tenet—his naturalistic view of the mind—can be safeguarding solely by rejecting inductivismand endorsing the hypothetical method. The result would be a philosophy whichpostulates the external world as an inference to an hypothetical explanation of pureexperience. Something still fails to ring true in that. More is needed: backing for the viewmentioned earlier, a view which may be thought of as in the spirit of Thomas Reid,though he did not give it the necessary backing—the view, namely, that there are normswhich are neither inductive nor deductive, but which defeasibly warrant experience-basedassertions about the physical world.MORAL FREEDOMThe necessary backing, showing how such defeasible warrants can obtain, could beprovided only by a philosophy which treats concepts, and the meanings of expressions ina language, as constituted by rules of use. This conception of concept and meaning is notpresent in Mill, though it could be reached by a sound progression from his naturalisticanalysis of logic, and his rejection of conceptualism, nominalism and realism. Its growthcan probably best be dated to the next generation of philosophers after Mill, and to theagenda of problems which they developed (partly at least in response to and reactionagainst Mill) at the end of the century; thus, to pragmatism, empirio-criticism, as also insome respects to neo-Kantianism and British idealism. That same conception opens upthe possibility of new responses to Mill’s problem about the method of inference to thebest hypothetical explanation—which was that in cases of genuine hypothesis we cannotbe certain that thereisa single best explanation.Though the roots of the required conception of concept and meaning date to thatperiod, how best to formulate it is still an open issue. Moreover the most difficult (thoughnot unconnected) question for the naturalist, that of giving an account of reasons, stillremains. As we have seen, it stands out as an obstacle for Mill when he needs to accountfor the authority of fundamental norms of reasoning. And it also stands out when he triesto show how, on the naturalistic view, it is possible for human beings to be morally free.This was a central issue for Mill. He deals with it as it appears in the classic question offreedom and determinism. His commitment to determinism was complete. But theconclusion drawn by others from that doctrine, that we have (in Mill’s phrase) no ‘powerof self-formation’, and hence are not responsible, properly speaking, for our character orour actions, would have destroyed the very centre of his moral convictions. Power todetermine one’s own purposes and hold to them, responsibility for one’s actions, are atthe heart of Mill’s ideal of life. ‘Moral freedom’, the ability to bring one’s desires underthe control of a steady rational purpose, is a condition of self-realization, of having acharacter in the full sense at all.So he must show how causally conditioned natural objects can also be rationallyautonomous agents. The sketch of a compatibilist solution which he provides in theSystem of Logicis brief but penetrating. He thought it the best chapter in the book. It iscertainly a worthy contribution to the great empiricist tradition, which dismisses theproblem as a perennially tempting confusion, to be dissolved by careful analysis.To describe determinism as the doctrine of ‘Philosophical Necessity’ is, Mill thinks,misleading. Not just because of the general empiricist point that causation is notcompulsion but for a more subtle reason; because ‘in common use’ only causes which areirresistible,whose operation is ‘supposed too powerful to be counteracted at all’ arecalled necessary:There are physical sequences which we call necessary, as death for want of foodor air; there are others which, though as much cases of causation as the former,are not said to be necessary, as death from poison, which an antidote, or the useof the stomach-pump, will sometimes avert…human actions are in this lastpredicament: they are never (except in some cases of mania) ruled by any onemotive with such absolute sway, that there is no room for the influence ofanother.(8:839)This is a general distinction, but Mill is right to think it important for the analysis of freeaction. It can be applied to motives; an action caused by an irresistible motive is plainlynot free. Without the distinction between resistible and irresistible causes, determinismturns into fatalism. We lose the sense of our moral freedom, which rests on the convictionthat the motives on which we in fact acted were resistible. We fall into the idea that wehave no power over our character; no ability to resist motives which we dislike or tochoose to act on those which we admire.Now incompatibilists will concede that changes in our character may result frombehaviour which is itself caused by the wish to change our character. But they will notconcede that this is a true case of ‘self-formation’, because they think the wish to changeour character is heteronomous: it comes from without. And they think that follows simplyfrom the fact that the wish is determined, ultimately if not proximately, by externalcircumstances. So Mill has to show that while the wish must indeed be determined, thatdoes not entail heteronomy. It can still bemywish.He cannot answer simply by invoking the distinction between resistible and irresistiblemotives. For a motive might perfectly well not be irresistible, in that it could be blockedby other motives—yet still be heteronomous. Something has to be added if we are tomove from the idea of my motives being resistible, in the sense that they could betrumped by conflicting motives, to the stronger idea that I have the power to resistmotives. That idea is the idea of rationality: the ability to recognize and respond toreasons. I act freely if I could have resisted the motive on which I in fact actedhad therebeen good reason to do so. A motive which impairs my moral freedom is one that cannotbe defeated by a cogent reason for not acting on it. The differ-ence between aheteronomous agent, driven by conflicting motives which are capable of checking eachother, and an autonomous agent who himself or herself resists the motive, lies in the factthat the latter responds to, and acts on, reasons.Acting from good reason is still acting from a motive which is causally determining.What matters is how the motive determines: it must be so related to the facts, as they arebelieved to stand by the agent, as to constitute a good reason and it must also be the casethat the agent acts on itasa reason. The same holds for the will to alter our character. Itmust indeed always be caused, and hence caused ultimately by circumstances we cannothelp. But it still satisfies the conditions of moral freedom, if it results from our graspingthat there is reason to change ourselves, and not, say, from indoctrination or obsession.Moral freedom for Mill is the ability to act on good reasons, as autonomy is for Kant;though Mill does not highlight the point as Kant rightly does. And of course it is not, forMill, transcendental. It is something I may have to a greater or less degree. I am more orless free overall, according to the degree to which I can bring my motives under scrutinyand act on the result of that scrutiny, I canmakemyself more free, by shaping mymotives or at least by cultivating the strength of will to overcome themA person feels morally free who feels that his habits or his temptations are nothis masters, but he theirs: who even in yielding to them knows that he couldresist; that were he desirous of altogether throwing them off, there would not berequired for that purpose a stronger desire than he knows himself to be capableof feeling…. we must feel that our wish, if not strong enough to alter ourcharacter, is strong enough to conquer our character when the two are broughtinto conflict in any particular case of conduct. And hence it is said with truth,that none but a person of confirmed virtue is completely free.(8:841)The person of confirmed virtue is the person who can conquer desires, when there isreason to do so, by a virtuous habit of willing. One must be careful not to assume thatMill, because he is an empiricist, is in the Humean tradition which holds reason to be aslave of the passions. We have already emphasized the difference between Hume’sscepticism about both theoretical and practical reason, and the naturalisticepistemological stance taken in different ways by Reid and Mill. In the practical as in thetheoretical case Mill is best understood not as denying the existence of categoricalreasons, in the sceptical style of Hume, but as quietly naturalizing them. He takes it thattalk of principles of theoretical and practical reason, and of our recognition of suchprinciples, is justified. But the fact remains that he does not explain how it is justified, ifnothing isa priori.He does not dramatize the issue, as Kant’s Critical philosophy does. And he does notconfront the Critical questions: what is it for a reason to exist, what is it to grasp a reason,how can reason be efficacious? But, on his own showing these questions must beanswered, in a fashion compatible with naturalism, if we are to make sense of ordinarycategories—reasoning, inferring, deliberating, deciding—categories which involvethinking of agents and reasoners as free followers of rationally given norms. For whileinference does seem to be a causal process it yet also appears to be something more than,or incommensurable with, a causal process. It seems to involve theacausalconsciousnessof a rule of reason. Precisely the same can be said for the rationalizing relation betweenmotive or deliberation, and free action or choice.NATURALIZED EPISTEMOLOGYThis Kantian argument, that naturalism cannot account for the rationality of experience,thought and action, was taken up by Mill’s idealist successors in Britain, led byT.H.Green. They elevated Hume, who was held to have perceived it, over Mill, who wasfelt to have hidden his face from it, or been unable to grasp it. And certainly Mill offersno thoroughgoing examination of what, on his own philosophy, the status of fundamentalnorms of reason is—how they can have objective authority. He merely takes it that theydo. The same applies to Reid. Like Reid, Mill assumes that any cognitive dispositionwhich is ‘ultimate’, original or spontaneous thereby underpins an objective norm. Wehave seen this in his treatment of beliefs based on memory, as well as beliefs based oninduction, and the same applies to his well-known derivation of what is desirable fromwhat is desired ‘in theory and in practice’. The similarity between Reid and Mill, on thisfundamental point of naturalistic epistemological method—the appeal to spontaneousdispositions which survive critical reflection—is easy to miss. It is obscured by theundeniably important disagreement between them in what they actually place on theirrespective lists of fundamental principles, as also by the intrusion of the controversybetween innatist and associationist psychology. But terms like ‘ultimate’, ‘spontaneous’,‘natural’, etc. need not mean ‘innate’—one must not confuse a phenomenon which isimportant for epistemological method—that of finding a principle naturally obvious—with a particular psychological explanation of its origin.The divergence between Hume’s sceptical naturalism, together with its Kantian andidealist sequels, and the naturalistic epistemology taken for granted by Reid, Mill andothers became a great divide in nineteenth-century philosophy. The most influentialphilosophers in the heyday of the analytic movement in the twentieth century stand alsoin the Critical rather than the naturalistic epistemological tradition. More recently,however, that has changed, largely through the influence of Quine. ‘Naturalizedepistemology’ is once more influential. The questions concerning it remain the same.Today, as in Mill’s time, one can ask whether thereisany route open to the naturalist,between Humean scepticism and Kantian idealism.If there is, it requires a sharper distinction than Mill, or indeed Quine, makes betweennorms and facts. Mill argued soundly from the naturalistic premiss, that nofactualstatement can bea priori.But the same is not true ofnormativestatements. Forallthatgrounds the objectivity of norms is reflective equilibrium and convergence—as indeedMill’s epistemological method implies. Having recognized this crucial point, one mayinnocently concede that statements about fundamental norms are—in a way Mill himselfcould have accepted, that is, a way which requires no transcendental or platonicmystery—a priori.Norms constitute the concepts which order our thought. Rationality,grasp of concepts, consists in sensitivity to them; it cannot therefore belong in the realmof the factual, any more than the norms themselves do. If this conception of concept andmeaning can be made out, we can endorse Mill’s naturalistic view of man.BIBLIOGRAPHYCitations of passages from Mill are by volume and page number of theCollected Worksof John Stuart Mill,ed. J.M.Robson (London and Toronto: University of Toronto Pressand Routledge & Kegan Paul, 1963–). The following volumes have been cited:4.1 VII, VIII,A System of Logic, Ratiocinative and Inductive: Being a Connected View ofthe Principles of Evidence and the Methods of Scientific Investigation,textual editorJ.M.Robson; introduction by R.F.McRae, 1973.4.2 IX,An Examination of Sir William Hamilton’s Philosophy and of the PrincipalPhilosophical Questions discussed in his Writings,textual editor: J.M. Robson,introduction by A.Ryan, 1979.See also:4.3 Ryan, A.J.S.Mill,London: Routledge and Kegan Paul, 1974.4.4 Scarre, G.Logic and Reality in the Philosophy of John Stuart Mill,Dordrecht:Kluwer, 1989.4.5 Skorupski, J.John Stuart Mill,London: Routledge, 1989.