Aristotle on Truth

The study of truth is surely among the crucial issues in both the philosophical tradition inherited from the Classics and modern philosophical debates. And the contribution of Aristotle in this field is acknowledged as the most influential from Antiquity onwards. We can then applaud the arrival on the scene of Paolo Crivelli’s (hereafter PC) book, which is the first monographic discussion of Aristotle’s theory of truth. The line of investigation pursued by PC is striking and powerful. Aristotle speaks of truth and falsehood in several works, but nowhere does he treat them extensively. With the acumen that is typical of those scholars interested in bridging the sometimes too evident gap between ancient and modern discussions of common issues, PC declares his intention to “engage” in a philosophical discussion with Aristotle. As he states, he is interested “in asking him some of the questions about truth which many modern analytic philosophers are interested in” (p. 39). Against the possible objection that PC could ask Aristotle questions that the philosopher never dreamt of, PC opposes a rigorous empirical methodology: starting from an analysis of the Aristotelian passages, he reconstructs the positions that Aristotle explicitly endorses, as well as those he is likely to be committed to. The result of PC’s approach is a book where, despite the wide-ranging theoretical dimension, all topics presented are explored in detail. Apart from a few sections discussed below, the book contains no superficial comments at relevant points, and the whole general discussion is conducted in considerable depth.

PC’s book consists of an introduction that, in addition to stating the author’s approach, presents a very useful overview of Aristotle’s theory of truth, and seven main chapters. The chapters are followed by six appendixes containing readings and translations of relevant passages of Aristotle’s text, as well as some formal presentations — aimed at formal logicians only — of crucial aspect of Aristotle’s theory. The book ends with a remarkably exhaustive bibliography, an index of names and index of passages.

Ch. I (“States of affairs, thoughts, and sentences”) examines what the items that Aristotle could consider as bearers of truth and falsehood are. In particular, as PC concludes on the basis of Metaphysics Δ 29 and Θ 10, these items are of three main kinds: objects (including state of affairs), mental items and sentences. Here I feel that the most compelling account is the section where PC deals with state of affairs (pp. 46-62). As he correctly argues, for Aristotle states of affairs are true or false in the strictest sense, insofar as they explain the truth and falsehood of items of other types based on them. Moreover, states of affairs have roles similar to those modern philosophers attribute to propositions but differ in one fundamental aspect: while there are negative propositions, for Aristotle there are no negative states of affair (p. 49). On this last point I have one reservation about the argument presented by PC since in the Categories Aristotle seems to postulate negative as well as affirmative states of affairs. It could surely be the case that, as PC shortly concludes, there was a development between the Categories and the Metaphysics. However, this is an important point that, because of its implication on other chapters of the book (especially ch. 4), should have been inspected more carefully. The chapter ends with a discussion of the truth-value of mental items and with a section supporting, with four cogent arguments (pp. 72-76), the idea that for Aristotle sentences are events that occurs over a relatively short portion of time: in light of this, sentences are expression-tokens and not expression types.

Ch. 2 (“Truth conditions for predicative assertions”) examines what truth conditions for predicative assertions Aristotle is committed to. After a digression on the nature of universals (pp. 78-82), PC addresses the issue of an apparent clash of de Interpretatione I, which says that falsehood and truth have to do with joining and separating, with Metaphysics Θ 10, which states that certain thoughts concerning non-composite items are true. According to PC’s interpretation, it is only where joining and separating are present that truth and falsehood are both possible. When thoughts involve neither joining nor separating, some are necessarily true, others necessarily false or neither true nor false (pp. 82-86). Sections 3 and 4 of the chapter — the least original parts of the book insofar as they are focussed on concepts already well-established in the literature — discuss Aristotle’s theory of assertion (in particular, the operations performed while asserting through affirmative or negative assertions) and the semantic theory of de Interpretatione 7. In the final section of the chapter, PC considers the passage of Metaphysics Ε 4 where Aristotle discusses the relationships between the operations of combination and division introduced by a predicative assertion and the categories (pp. 95-98). In an attempt to explain Aristotle’s claims there that the investigation of beings qua beings, corresponding to the categories, can ignore what is in the sense of being true, PC concludes that the things that correspond to the categories are prior to what ‘is’ in the sense of being truth both in respect of nature and in formula. This conclusion justifies a dependence of truth on the categories and leaves truth outside the domain of a metaphysical investigation.

As a way to complement Chapter 2, Chapter 3 (“Truth condition for existential assertions”) explores the field of existential assertions. Following Aristotle’s understanding, PC focuses on two types of existential beliefs and assertions: those concerning simple items (essences and incorporeal substances such as God and the intellect) and those concerning material substances. As for the first type, PC, on the basis of Metaphysics Θ 10, shows that as a consequence of their everlasting characters existential assertions are always true or false (pp. 100-116). Since, material substances, on the contrary, do not last forever, existential assertions about them can vary in their degree of truth, and thus be true at one time and false at another. Here, PC, with fine observation, and against the traditional interpretation, argues in favour of treating material substances as composite items alongside states of affairs. For a material substance to exist is, in fact, for its form to hold its matter (pp. 121-125).

Chapter 4 (“Truth as correspondence”) is where PC’s argumentation works extremely well. The chapter, which deals with an assessment of Aristotle’s theory of truth as a correspondence theory, is surely among the main contributions of the book, and it is most relevant to today’s discussions in the field of philosophy of logic. The main problem underlined by PC is that, for the classical interpretation, a correspondence theory of truth for assertions would require that an assertion is true (false) just in cases where there is some (no) fact to which it corresponds. But Aristotle does not mention facts. Nor does he mention, at least according to PC’s interpretation, negative states of affairs as a basis for a second conception of the theory. For Aristotle, the claim of a theory of truth as correspondence derives from taking the truth of an assertion to amount to a relation of isomorphism to reality (pp. 130-138). Two formats of this theory — where the components of reality with respect to which a true assertion of isomorphism holds are objects or predicative assertions — are then presented and discussed. Having established the correspondence-as-isomorphism conception, as PC defines it (p. 132), the author does not avoid tackling the troublesome paradox of the Liar that seems to invalidate the idea of this conception (pp. 139-151). Since it is not clear whether Aristotle himself did give a solution of the paradox, PC bravely attempts to reconstruct Aristotle’s possible position on the matter. By exploring the class of expressions used absolutely or with some qualification, PC concludes that for Aristotle an utterance of “I am speaking falsely” is sometimes neither true nor false.

The topic of vacuous terms, defined by PC as terms that fail to signify an item of the appropriate kind (p. 152), are treated in Ch. 5. Indeed these terms create another obstacle to the idea of an expected correspondence between truth and reality. For PC, Aristotle considers the predicates and subjects of predicative assertions as non-vacuous. PC gives four arguments in support of this interpretation, among which the third one is the most convincing: since for Aristotle predicates and subjects signify members of the categories, they are non-vacuous insofar as the members of the categories exist (pp. 154-155). But PC’s interpretation goes further and shows that, for Aristotle, predicates and subjects of predicative assertions are never empty: they always signify existent items (pp. 158-163). But what then about utterance like “A goat is a goastag”, where the predicate seems to be empty? PC conducts here an investigation that I found hard to contextualise because of the far too rich mix of linguistic and logical aspects considered. By exploring the possibility that for Aristotle an utterance can coincide with one or more assertions, according to a disambiguation-interpretation (p. 166), PC’s main idea is that utterances containing seemingly empty terms are not genuine predicative assertions but are composite assertions whose components are linked by connective particles.

The last two chapters of the book deal with the relationship between truth and time, one that is also prominent in current discussions of temporal logic. In Ch. 6 (“Truth and change”), PC defends Aristotle’s ideas that the bearers of truth and falsehood are expression-tokens, arguing against the claim that bearers of truth and falsehood can be true at one time and false at another (pp. 183-189). PC offers an example showing that indeed an utterance can have different truth values at different times (pp. 185-6). But this is surely a point that PC could have discussed more extensively, especially if we consider that most of the critics understand this point as in inconsistency in Aristotle’s thought. PC concludes the chapter by bringing some light to another claim of Aristotle concerning the relational character of truth (pp. 189-194). By recalling certain aspects of modern ‘minimalist’ theories of truth, PC shows that for Aristotle truth is not a genuine property but has more the characteristics of a relation. The fact of being a relation for PC explains the reason why for Aristotle if an assertion is true at one time and false at another, it has not changed itself: indeed what is responsible for the different truth-values of a predicative assertion is the object it refers to, an object that might change during an interval of time. The related discussion of the problematic issue of bivalence and determinism is addressed in Ch. 7 (“Truth and Determinism in de Interpretatione 9″). On the one hand, Aristotle rejects Bivalence, and refutes Determinism, by stating that some future-tense singular assertions are sometimes neither true nor false and could remain without truth-value forever (see for example an utterance like “A sea-battle will take place tomorrow”). On the other hand, he seems to be committed to accept the Excluded Middle for future-tense assertions like “a sea-battle will take place tomorrow or it is not the case that a sea-battle will take place tomorrow”, which are always true. As PC contends, these positions are consistent and reasonable. In particular, Aristotle’s defence of the Excluded Middle does not commit him to Determinism: if, in fact, ‘it is now necessary that tomorrow a sea-battle should either take place or not take place’, the necessary operator should not be distributed over the disjunction.

In sum, PC’s book is without question an impressive and important work of scholarship. It is a book that deserves to become a standard study of the topic. As I have already said, I am also pleased to find a book where the author attempts a rediscovery of the classical tradition while paying attention to modern theories and expectations. At this stage, however, I also have a less positive comment to make on the style of the book. In reading PC’s work, one notes that the author has the tendency to spell out every point, even if it is already well-established in the literature, and discuss everything, even if peripheral. In the book there are also numerous repetitions as well as several formalisations of Aristotelian passages that sometimes prevent the reader from fully appreciating the passages themselves. My fear is that this presentational weakness may discourage careful reading of the book and rob it of the impact it deserves.