MIND–WORLD IDENTITY THEORY AND SEMANTICREALISM: HALDANE AND BOULTER ON AQUINAS

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In a recent article, Stephen Boulter takes issue with John Haldane’s proposedaccount of the relationship between mind and world based on Aquinas’ theory ofcognition.1 While accepting the direct realism of Haldane’s theory, according towhich mind and world are (potentially) structurally identical, Boulter argues againstHaldane’s attempt to square metaphysical realism with semantic anti-realism. Hehas three main objections. First, Haldane’s Aquinas would be a truncated one, i.e.,only a truncated reading would support the suggestion that Aquinas holds meta-physical realism (hereafter MR) in conjunction with semantic anti-realism (SAR).Secondly, the ‘complete’ Aquinas does not in fact accept SAR. Thirdly, Aquinas’MR and SAR are incompatible. In considering these objections, I shall argue thateven if MR and a full-bodied SAR may be incompatible, from the stance of themind–world identity theory, one may nevertheless maintain MR together withthe negation of semantic realism (SR). Further, I shall suggest that this is what Hal-dane actually claimed, and moreover that Aquinas would have accepted it.

I

Haldane’s Aquinas holds (a) that one can talk about x only if one’s intellect is inconformity with it. Boulter (p. ) emphasizes (b) that Aquinas really recognizestwo ways of acquiring knowledge of the natural world:

one can come to know something directly by being literally informed by the object inquestion in the manner Haldane has discussed; or one can come to form some idea ofthe existence and nature of something indirectly by noting its effects. It is this secondmode of knowing (much the poorer of the two) which Haldane has ignored.

It is contentious that (b) is inconsistent with (a). Even if it were true that Haldanedoes not deal with indirect knowledge (cf. Haldane p. ), (a) merely claims that onecan think about x only if one has the relevant concepts. There is no restriction of theways in which one may arrive at those concepts, i.e., whether only directly or alsoindirectly. Even if an account of indirect knowledge may still be needed, (a) does not

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1 S.J. Boulter, ‘Could Aquinas Accept Semantic Anti-Realism?’, The Philosophical Quarterly, (), pp. –; J.J. Haldane, ‘Mind–World Identity Theory and the Anti-Realist Chal-lenge’, in J. Haldane and C. Wright (eds), Reality, Representation and Projection (Oxford UP, ),pp. –.

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imply the impossibility of such an account. Accordingly one could endorse Aquinas’claim that cognition requires formal identity between mind and thing, and at thesame time suggest that it is possible to possess the form of something one has notdirectly encountered. Haldane’s Aquinas may need to be completed, but it isnot clear that he is truncated.

II

According to Boulter, the second mode of knowledge, indirect knowledge, is im-portant both for science and natural theology, and it entails that ‘according toAquinas, one can understand a proposition p without ever being able to recognizethat p, a direct contradiction of SAR’. In support of this claim he notes (p. ) thatAquinas allows one can know something through mere acquaintance with its effects:

one will be able to claim partial knowledge of x, perhaps no more than that x exists(unless the effect is adequate to the cause, i.e., a member of the same natural kind).But this is enough to formulate theories concerning the nature of x, as the history ofscience clearly illustrates.

An example might be force fields: we have experience of bodies moving throughregions of space in ways which can best be accounted for if we postulate the exist-ence of particularly structured forces in those regions. However, our knowledge ofthose forces is imperfect: we do not know what they are nor what encounteringthem would be like, we know only their effects. According to Boulter, Aquinas canallow this kind of knowledge only because he endorses SR. In summary structure,Boulter’s argument is as follows (pp. –):

. One can come to know something directly by being literally informed by theobject in question ... or one can come to form some idea of the existence andnature of something indirectly by noting its effects

. The effects of an unobserved x serve as the nominal definition (or significatio nominis)of x, and when x is used in a proposition the term is initially taken to mean nomore than ‘the cause of certain effects’2

. Once the existence [of x] has been established, one can move on to formulatesome idea of its essential characteristics [according to Aquinas, terms for ob-servable entities can be applied to unobservable ones through analogy].

Therefore

. This semantic theory ... provides a way of conceiving of entities known im-perfectly through their effects; it does not extend one’s recognitional capacities

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2 The expression ‘serve as’ is ambiguous: it may taken to mean either that the effects of anunobserved x are its significatio nominis, or that they can be used instead of the proper significationominis when this is unavailable because x is unobservable. The latter seems to be the correctinterpretation, if consistency with () is to be maintained: a proper nominal definition of athing defines what sort of thing it is, and this can only be given when the essential character-istics of that thing are determined.

MIND–WORLD IDENTITY THEORY AND SEMANTIC REALISM

. [Consequently] it is not necessary that one be able to recognize that p, even inprinciple, in order to understand the proposition p.

Claims ()–() are paraphrases from Aquinas, claims () and () are conclusionsdrawn by Boulter. The crucial point seems to be (), especially its second conjunct,since if this is conceded, the defeat of the conjunction of MR with the rejection ofSR seems to go through. Claim (), though, is ambiguous. First, if it is taken literally,the second conjunct of () says that Aquinas’ semantic theory does not improve therecognitional capacities of speakers. If this were the claim, it would be not only un-surprising but trivial, for it is not the task of a semantic theory to improve speakers’conceptual abilities by allowing new uses of their language. Furthermore, on thisreading, () does not entail (), since the idea that a semantic theory allows themeaningfulness of analogical uses of terms, conjoined with the idea that the sametheory does not improve the recognitional capacities of speakers, does not entail thatspeakers must be able to understand propositions for which they lack recognitionalcapacities. For the recognitional capacities associated with the literal uses of termscould be also at work when the terms are used in an analogical sense, at least for therespect in which the analogical use is not completely ambiguous. Some furtherargument is needed to show that this is impossible.

Secondly, if () is taken less literally, it may be seen as claiming that Aquinas’semantic theory concedes that the terms of a language can be used on occasionswhere they go beyond their literal meaning, i.e., used analogically, even if it does notconcede that the recognitional capacities of speakers are wider than is normallythought. ‘Normally thought’ by whom? Since this is said in reference to Aquinas’semantic theory, and since the core of that theory is Aquinas’ thesis on analogy, thenthe answer seems to be ‘by those who do not accept the thesis that language can beused analogically’. Would () follow from ()–() on this reading? It seems that thereis nothing in ()–() which prevents one from holding that the recognitional cap-acities of speakers are extended when they are also able to speak analogically. Asemantic anti-realist, who believes that understanding a sentence is a sufficient con-dition for having the capacity necessary for recognizing its truth-conditions, couldthus consistently accept ()–(). In order for () to follow from ()–() one must firstreject anti-realism. Therefore, as an argument against the possibility that Aquinascould accept the thesis of the semantic anti-realist that conception is co-terminouswith recognizability in principle, ()–() is question-begging.

Boulter backs up his reasoning with examples taken from Aquinas’ considerationsabout science. According to Aquinas, in some cases our arguments cannot provetheir conclusion with certainty. They do not produce science (scientia), in the sense ofa system of deductive demonstrations, but opinion or belief, i.e., they can onlyestablish a ‘possible solution’ (‘science’ here must not be taken in the modern sensediscussed above: in Aquinas’ terms, the unobservable entities of contemporaryphysics would probably be objects of possible solutions, rather than objects of‘science’). Boulter comments (p. ):

when one ‘arrives at’ a possible solution one has simply recognized what could be thecase – one has no warrant to assume that the possible solution represents what actually

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is the case. The points of concern for us ... are (a) that by definition, a possible solu-tion is a theory whose truth-value eludes us; and (b) that all we can produce concern-ing entities inaccessible to sense observation is a possible solution. However, one hasevery reason to believe that Aquinas maintains that one understands these propositions,despite the fact that, in principle, we can never determine their truth-value.

There are at least three remarks to be made about this. First, prima facie, thisseems a strange consideration. If the fact that Aquinas allows that some of ourclaims lack certainty were enough to make him a semantic realist, then it wouldmean that the semantic anti-realist has no resources with which to draw a distinctionbetween belief and knowledge. This would be contentious, to say the least.Secondly, with regard to (a), Aquinas could maintain that the truth-values of thepropositions of a theory may elude us because they are evidence-transcendent, orbecause they are undecided. If the latter disjunct is accepted, Aquinas’ view wouldbe compatible with semantic anti-realism. Thirdly, (b) seems false, since there arecounter-examples to be found in Aquinas: especially apt, perhaps, is the fact that hebelieved the existence and some attributes of God to be demonstrable with certainty,even though God is not an object of the senses.

Boulter raises the interesting case of the anti-realist rejection of bivalence andAquinas’ treatment of future contingents. He claims that Aquinas does not rejectbivalence, and therefore accepts semantic realism. Is this a proper reading? Accord-ing to Aquinas, ‘“true” signifies that what is the case is said to be the case, a thing[being] true in the way in which it is or exists.... But when something is yet to come,it does not exist in itself .’3 Future contingents do not exist in themselves, but insomething else, i.e., in a mind. Consequently when a mental content is about afuture contingent, reality lacks those facts which may decide if that content is a goodrepresentation or not. Thus a statement about a state of affairs which does not yetexist cannot be said to be true or false, i.e., to have a truth-value: its truth-value isnot decidable. If this reading is plausible, then Aquinas’ view may not clash withanti-realism.

It may be countered that this holds only for future contingents. Given Aquinas’theory of truth, the truth-values of statements concerning the far past may bedecided even when the truth-conditions of those statements are beyond ourrecognitional abilities. Something which was the case had existence in itself, to useAquinas’ expression, and so it can truly be said to have been the case, even if thetruth-value of a statement which expresses it transcends our recognitional abilities. Ifthis is so, then Aquinas and the semantic anti-realist do disagree after all: for wouldnot the anti-realist maintain that the truth-values of statements beyond our recog-nitional capacities are undecided?

At this point the mind–world identity theorist may distinguish two senses inwhich something may be said to be beyond our recognitional capacities: in the firstsense, we cannot recognize it because we lack the relevant concepts or the intel-lectual ability to form them; in the second sense, we cannot recognize it because wecannot have empirical access to it. Thus, against the semantic realist, mind–world

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3 Peri Hermeneias xiii –, quoted by Boulter p. .

MIND–WORLD IDENTITY THEORY AND SEMANTIC REALISM

identity theorists may accept that we cannot understand statements that transcendour recognitional capacities in the first sense, but may not follow the semantic anti-realist in requiring that recognitional abilities in the second sense are also needed forunderstanding. In this way they may object to SR without embracing at the sametime a full-bodied SAR. This seems consistent with Aquinas’ views as consideredabove, and seems also to be Haldane’s point. He does not claim that he is an anti-realist, but only that an anti-realist and a supporter of his view may be allied inarguing against the conception of truth of a metaphysical realist who does not holdthe mind–world identity thesis (cf. Haldane p. ).

III

The kind of metaphysical realism proposed by Haldane is marked by the idea thatmind and world are structurally identical, which means that the wide contents ofthought are intrinsically representational and that the world is intrinsically intel-ligible. Haldane’s debts to Aquinas, though, seem to force him to accept otherThomistic theses, such as the idea that the human intellect cannot know all of cre-ated reality, and that truth and reality are convertible. The latter claim means thatthe set of all possible true sentences represents all the facts which exist in the world.From these two premises, Boulter quite rightly draws the conclusion that there aretruths concerning external reality that are beyond human knowledge. The latterclaim, though, seems to be in tension with the thesis that the world is intrinsicallyintelligible. Boulter suggests (p. ) that only the acceptance of SR can reconcilethese two claims:

the portion of reality which lies within human purview is rendered intelligible only ifone is able to posit the existence of causal entities and processes lying beyond the im-mediate recognitional capacities of human beings.

This conclusion can be avoided if one notes that what the thesis of the intrinsicintelligibility of the world implies is that the world is conceptualizable or thinkable.It is consistent with this implication that the world may be only partly intelligible tohumans. Intelligibility and intelligence, on this view, come in degrees. The moreintelligent subjects are, i.e., the more extended and profound their recognitionalcapacities are, the wider the part of reality available to them will be. Given themind–world identity thesis, there will be no room for the traditional scepticismoriginating from the conjunction of MR and SR. Since knowledge in less thanomniscient beings is possible because of a partial identity between the world andtheir minds, there is no risk that the addition of further information about the worldmay cause all of their beliefs to be false. ‘Further information’ here does not referto the facts which have not yet been encountered but which belong to a kind forwhich the subjects already have the relevant recognitional capacities (in either senseof this expression). For we are already assuming ideal epistemic conditions for thesubjects. Rather the further information in question is the availability of a portion ofreality which was not open to the subjects before, i.e., it is due to an improvement

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of their recognitional abilities. The new information will enlarge their recognitionalcapacities (i.e., make their minds more extensively identical to the world), and allowthe discovery of new truths besides those already acquired.

At this point a metaphor may be helpful. If we want to reproduce an object, wemay decide to take a cast or imprint of it. If we use finely grained plaster, the castwill reproduce all the smaller details of the object. If on the other hand we userougher clay, the cast will miss some of the surface details of the object. Both castsare reproductions of the object, reproducing its shape and structure. But the formerdoes so in greater detail than the latter, i.e., with regard to surface structure itexhibits a more extensive isomorphism. Similarly, the limitations of human concep-tuality lie on the side of the intellect, not on the side of reality. The claim that theworld is necessarily such as may be fully comprehended does not imply either that itis, or even that it may be, fully known by us.

In conclusion, it can be said that, from the standpoint of mind–world identitytheory, MR is consistent with the rejection of a full-bodied SR, since the mind–world identity theorist may maintain that there is nothing in reality which cannot beconceptualized, while agreeing that not all truths can be empirically known. As wehave seen, this is consistent with Aquinas’ semantic conception, which involves theanalogical use of terms, and may be suggested by his views about future contingents.

Finally, this is all that Haldane claimed, since, as we have seen, he did not try tosupport SAR, but only to show that some of the anti-realist complaints against SRmay also be accepted by a mind–world identity theorist.4

University of St. Andrews and University of Padova

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4 I would like to thank John Haldane, and anonymous referees of The Philosophical Quarterly,for their comments on a previous draft of this paper.

MIND–WORLD IDENTITY THEORY AND SEMANTIC REALISM