"Almost everyone knows that it was Aristotle who proposed the classical (or correspondence) theory of truth for the first time. However, the fact that his writings contain different
and often mutually non-equivalent statements on truth is less recognized. This is a sample of Aristotelian explanations concerning the concept of truth (...):
(3) To say of what is that it is not, or of what is not that it is, is false, while to say of what is that it is, and of what is not that it is not, is true (Metaphysics
(4) The fact of the being of a man carries with it the truth of the proposition that he is; and the implication is reciprocal: for if a man is, the proposition wherein we allege
that he is, is true, and conversely, if the proposition wherein we allege that he is true, then he is. The true proposition, however, is no way the cause of the being of the man, but the fact of the
man's being does seem somehow to be the cause of the proposition, for the truth or falsity of the proposition depends on the fact the man's being or not being (Categories 14 b).
(5) But since that which is in the sense of being true or is not in the sense of being false, depends on combination and separation, and truth and falsity together depend on the
allocation of a pair of contradictory judgements; for the true judgement affirms where the subject and predicate really are combined, and denies where they are separated, while the false judgement
has the opposite of this allocation (Metaphysics 1027 b).
(6) he who thinks the separated to be separated and the combined to be combined has the truth, while he whose thought is in a state contrary to that of the objects is in error
(Metaphysics 1051 b).
(7) It is not because we think truly that you are pale, that you are pale, but because you are pale we who say this have the truth (Metaphysics 1051 b).
(8) Propositions correspond with facts (Hermeneutics [De interpretatione] 19 b).
The formulation (3) is usually taken as Aristotle's official definition of truth. Now (4) repeats the content of (3) but adds that being is in a sense more basic for truth than an
assertion which is qualified as true. The two statements are not equivalent because neither does (4) follow from (3) nor does the reverse entailment hold. Statements (5) and (6) introduce an explicit
ontological parameter, namely combination and separation; these statements seem to be equivalent (or at least "nearly" equivalent).- On the other hand, there is no direct entailment from (5) (or (6))
to (3) or (4), and back.
Perhaps one might say that "a is b" is true if and only if the relation which holds between referents of a and b is mapped by the relation holding between a and b, and false if the
mapping is not in case. If we decide to label mapping as "combination" and not-mapping as "separation", we obtain something very close to (5) and (6). And if we look at combination as correspondence
and separation as non-correspondence, (5) and (6) become popular formulations of the classical definitions of truth.
The statement (7) seems to exemplify previous explanations, particularly (3). Finally, (8) explicitly speaks about facts and correspondence but it is only a marginal remark made by
Aristotle when he considered the celebrated sea-battle problem. Hence, there are no sufficient reasons to treat (8) as a serious proposal to define the concept of truth.
If we take (3) as Aristotle's official truth-definition (and, a fortiori, as the first mature explanation of CCT; [Classical Concept of Truth]), than other Aristotelian
formulations should be understood rather as more or less auxiliary comments than proper definitions of truth. The point is very important because no idea of correspondence is directly involved in
(3). Although, as my previous remarks show, "combination" can be replaced by "correspondence" but nothing forces us to dress Aristotle's truth-theory into "correspondence talk". In fact, (3)- 7) may
be explained without any reference to such ideas as correspondence, agreement, adequacy or conformity; recall that (8) is only a marginal remark. I think that the best understanding of what is going
on in Aristotle's theory of truth consists in looking at (3) as something which is very closely related to (1) and (2). Then if we think of Plato's philosophy of truth as a further step in the
tradition beginning with old Greeks poems and continued by the Pre-Socratics, Aristotle should also be considered in the same way. Under this assumption, (3) schematically says how to answer the
question: how is it? Although Aristotle supplements (3) with considerable ontological equipment, his main intuition concerning the concept of truth seems very simple.
Various explanations by Pierre Abélard of the concept of truth offered in his Logica Ingredientibus lead to (see De Rijk [Petrus Abaelardus Dialectica - Assen,
1956] p. LIV):
(9) the sentence p is equivalent with "p is true" if and only if p is the case. Clearly, (9) anticipates the semantic definition of. truth but it was not properly understood in the
Middle Ages (nor later).
The most famous medieval explanation of the concept of truth comes from Thomas Aquinas. His formulation is this:
(10) Veritas est adaequatio intellectus et rei, secundum quod intellectus dicit esse quod est vel non esse quod non est (De Veritate 1,2).
The passage which begins with the word secundum, is simply a repetition of Aristotle's main formulation (see (3) above). But the first part of (10) -- veritas est
adaequatio intellectus et rei -- is an obvious addition to Aristotle, actually related to (5) or (6). Usually, (10) is quoted in its simplified version limited to its first part: veritas est
adaequatio intellectus et rei; in fact, this shortened formula is the most popular wording of the classical truth-definition. However, everybody who employs this simplified record of CCT as
"Aristotelian", must remember that it is certainly not Aristotelian to the letter. The question whether and to which extent it is Aristotelian in spirit requires special investigations that exceed
the scope of this paper. So I restrict myself to some remarks on adaequatio intellectus et rei.
One can link the meaning of adaequatio in (10) with the second (Aristotelian) part of this formula. However, Aquinas also uses such terms as conformitas,
correspondentia and convenientia to explain his understanding of CCT. It suggests his adaequatio expresses (or at least might express) a content which is not
quite reducible to Aristotelian intuitions.
What is going on in the first part of (10)? There are several possible answers. Let me indicate three. Firstly, veritas est adaequatio intellectus et rei may be regarded as
a counterpart of (5) or (6). Secondly, the fact that the adaequatio-formula opens Thomas' definition seems to suggest that he changed the centre of gravity in the Aristotelian truth-theory
in such a way that adaequatio, correspondentia, conformitas or convenientia became crucial ideas in defining truth. Thirdly, the adaequatio-formula was invented by the
Schoolmen to capture intuitions concerning truth in a simple way; the Schoolmen very much liked brief formulations. It is very difficult to decide today which interpretation (I am very far from
claiming that my three cases exhaust all possible interpretations of (10)) is correct with respect to Aquinas' original intentions. However, the next development of Thomism rather followed the second
interpretation. For instance, Francisco Suárez says that veritas transcendentalis significat entitatem rei, connotando cognitionem seu conceptum intellectus, cui talis entitas conformatur vel in
quo talis res representatur (Disputationes metaphysicae, 8, 2.9). The content of (3) is completely absent in Suárez. He proposes instead an analysis of truth with the help of the
concept of representatio and seems to assume that a conformitas (adaequatio, correspondentia) holds between thoughts and their objects. That is what I mean by "changing the centre
of gravity". Most post-medieval thinkers adopted this route in their thinking on truth and tried to explain how adaequatio should be understood.
It is now proper to introduce an important distinction (see Wolenski-Simons ), namely that of weak and strong concept of correspondence. If the concept of correspondence is
governed by (3) (or similar statements), we are dealing with correspondence in the weak sense. On the other hand, Suárez's approach employs correspondence in the strong sense. I am inclined to regard
the distinction of the two concepts of correspondence as fairly crucial for the history of CCT. Thus, we must always ask which concept of correspondence is used in particular truth-theories because
many difficulties with interpreting philosophers' views on truth are rooted in their view of the distinction in question. As far as the matter concerns the concept of correspondence, it has been
explained by notions like sameness, similarity, model, picture, co-ordination, isomorphism or homomorphism (...).
Let me finish this section with some historical remarks (see Gilson ). Aquinas notes that his definition of truth is derived from Liber de definitionibus by Izaak ben
Salomon Israeli; Aquinas also refers to Avicenna in this context. However, adaequatio does not occur in Israeli's truth-definition which (in Latin version) is this: Et sermo quidem
dicentis: veritas est quod est, enuntiativus est nature veritatis et essentiae ejus, quonian illud sciendum quod es res, vera est; est veritas nonnisi quod est; this formula is fairly
Aristotelian. Avicenna in his Metaphysics says (in Latin translation) that veritas [...] intelligitur dispositio in re exteriore cum est ei aequalitas; the last word suggests the
strong sense of correspondence. It was William of Auvergne who introduced the term adaequatio in philosophy for the first time. He refers (in De universo) to Avicenna in the
following way: et hoc [intentio veritas] ait Avicenna, est adaequalio orationis et rerum. Then William adds that the truth is intellectus ad rem. In Albertus Magnus' treatise De
bono we find that truth is adaequalio rei cum intellectu. Then comes (10)." (pp. 141-144 of the reprint).
From: Jan Wolenski - Contributions to the history of the classical truth-definition. In Logic, methodology and philosophy of science Vol. IX. Amsterdam: Elsevier 1994. pp.
481-495, Proceedings of the Ninth International Congress of Logic, Methodology and Philosophy of Science, Uppsala, Sweden, August 7-14, 1991.
Reprinted in: Jan Wolenski - Essays in the history of logic and logical philosophy - Cracov - Jagiellonian University Press 1999 pp. 139-149.
"In the Summa Theologica (I, q. 16; a. 2, ad 2) of St. Thomas Aquinas we read: "Praeterea, Isaac dicit in libro De efinitionibus, quod "veritas est adaequatio rei et
intellectus"." Also in his De Veritate, q. 1, a. 1, we find the statement: " Et sic dicit Isaac, quod veritas est adaequatio rei et intellectus ".
B. Geyer in his work, Die Patristische and Scholastische Philosophie (Berlin, 1928), p. 334, says " Bonaventura, Heinrich von Gent, Thomas von Aquin entnehmen die bekannte
scholastische Wahrheitsdefinition: veritas est adaequatio rei et intellectus dem "Buch der Definitionen Isaaks. " He gives a reference to St. Bonaventure's commentary on First Book of Sentences (d.
40, a. 2, q. 1) where the definition is found. It is not there attributed to Isaac by St. Bonaventure and the footnote referred to below. is repeated distinctly saying it does not occur in Isaac.
In the work S. Thomas d'Aquin by A.-D. Sertillanges (Paris, 1910) Tome I, p. 41, we read: "Quant à celle d'Isaac, que saint Thomas semble affectionner par-dessus les autres: "La
vérité est l'adéquation des choses et de l'intelligence" (adaequatio rei et intellectus), c'est une définition à double entente." J. de Tonquédec, in his La Critique de la Connaissance
(Paris, 1929, p. 512) says : " Le vrai, dit Isaac, est l'équation de la chose et de l'esprit ", and in a footnote it is stated: "La définition de la vérité se trouve dans le Livre des
Définitions, comme le dit saint Thomas."
In the Encyclopedia Britannica (ed. IV, 1929, it is not in the 1910 edition) s. v. Israeli, Isaac Ben Salomon we read: " Through the labours of Gundissalinus he
became very popular with the thirteenth century scholastics who took from his definitions the famous definition: veritas est adaequatio rei et intellectus. (1)" (...)
Several other references might be given to modern writers on mediaeval philosophy who attribute the definition to Isaac.
Among mediaeval writers, St. Albertus Magnus attributes the following definition of truth to Aristotle: " Dicit enim Aristoteles in V primae philosophiae, quod "veritas est
adaequatio rerum et intellectuum" " (Summa Theologica, P. II, Tr. 1; q. 1; m. 2; a. 1, Arg. 4.). Moreover he gives Isaac's definition of truth as follows: " Complexi autem sermonis veritas
est secundum Isaac in libro de Definitionibus, affirmatio rei de qua vere praedicatur, vel negatio rei de qua vere negatur. " (I. Sum. Theol., Tr. VI, q. 25, m. 1). " Et hoc modo veritas, ut dicit
Isaac in libro de definitionibus, quod veritas non est nisi quod est et quod res vere est. " (I. Sum. Theol., T. 6, q. 25, m. 1). " Dicit enim Isaac quod "veritas est id quod est res", vel secundum
aliquos, "veritas est sermo quem confirmat demonstratio". " (I. Sum. Theol., T. 6; q. 25, m: 2.). " Secundum Isaac et secundum Augustinum, verum est id quod est. " (Ibid. No. 3.). " Et secu idum hoc
dicit Isaac, quod "veritas est sermo quem aff rmat demonstratio vel sensibiliter vel actualiter. " 1. Sum Theol., T. 6, q. 25, m. 1.
St. Bonaventure quotes the definition "adaequatio rei et intellectus" several times, (v. g. Sent., Lib. I, D. 40; Art. 2; q. 1. Sent., Lib. I, D. 46; Art. 1; q. 4. Sent., Lib. II,
D. 37; Art. 2; q. 3. In Hex. Collationes, III. par. 8), but so far as I have discovered, he does not state where it is to be found.
In the Quaracchi Edition of his works (1882), Tom. I. p. 707, note 5, the editors call attention to the fact that they had read one ms. of Isaac (Monac. B. R. 8001, ff. 151v.-154r.)
without finding the definition of truth which St. Thomas attributes to him. They quote from Isaac a definition which will be referred to later on. In several other places where St. Bonaventure quotes
the definition veritas est sermo quem confirmat demonstratio, they refer the reader to this note or repeat it in full.
I have just finished reading three mss. of Isaac De definitionibus, viz. (a) Paris B. N. 6443, ff. 187r-190r; (b) Paris B. N. 14700, ff. 153r-160v. Catalogued as belonging
to the XIII. century, it bears the book-mark of the Abbey of St. Victor in Paris. (...) In none of these mss. did I find the definition of truth so persistently attributed to Isaac.
On f. 156v, 14700, there begins a long list of definitions which continue to the end of the work. This list is also in 6443, but the Vatican ms. lacks it. In these mss. Isaac gives
the following definitions of truth: 1. "Diffinitio namque veritatis est quod est ; et diffinitio vani tatis est quod non est aliquid aut, narratio rei absque eo quod est." 14700, f. 155r. C. 1, 11.
12-13; 6443, f. 147v. C. 2, 11. 45. The Vatican ms. reads the same except that it has autem for namque, and falsitatis for vanitatis. (F. 47v. C. 2, 11. 25 sq.)2. Diffinitio veritatis; and there is
written in the margin, by the same hand I think, veritas est quod est res. And then the text goes on: " et diffinierunt eam disertores. Dixerunt enim, veritas est sermo quem firmat demonstratio aut
sensibiliter aut intellectualiter. ... hec diffinitio est assumpta ex qualitate veritatis, non ex eius quiditate. Et illud ideo, quoniam cum aliquis dicit quid est veritas, est responsio in eo est
quod est res, et cum dicit qualis est, dicitur ei quod est sermo quem demonstratio firmat aut intellectualiter aut sensibiliter... et sermo quidem dicentis veritas est quod est enuntiativus est
nature veritatis et essentie eius, quoniam illud secundum quod est res, vere est veritas, non nisi quod est. ... falsitas est non quod est res, et dicitur falsitas, narratio rei cum diverso quod est
ipsa et ipsius . contrario. " (14700, 158v, C. 2, 11. 30 sq.) Ms. 6443 is a very poor text. The above passage is faulty but the important parts relative to this question are the same. In the margin
of 189r. C. 2, 1. 21 there is written in the first hand: " diffinitio veritatis; veritas est quod res est, " and in the same column 1. 39, we read: " sermo quidem dicentis: veritas est quod est
essentiativum (sic) est nature veritatis et essencie eius quoniam illud secundum quod est res vera est; est veritas non nisi quod est. "3. " Verum est affirmare rem rei cui est secundum veritatem aut
expellere rem a re a qua vere removetur. ... Falsum est affirmare rem rei que ab ea removetur vere et removere rem a re que ei affirmatur secundum veritatem. " (14700, 159 r. C. 1, 11. 22 sq. = 6443,
189r C. 2, 11. 48 sq.) Monacensis 3001 as quoted in the Quaracchi Edition varies somewhat in wording from the above, but the meaning is much the same.
The definition of verum (number 3) perhaps comes nearest to the definition ascribed to Isaac by St. Thomas, yet it is by no means the same either in meaning or language. Perhaps
some reader may know of a different manuscript tradition of Isaac wherein the classic definition is found."
(1) The statement in the Encyclopedia Britannica might lead one to believe that Gundissalinus quoted the definition from Isaac. I have also read recently a ms. of
Gundissalinus De anima, Vat. Lat. 2186, f. 104r.-119v. I found there this definition of truth; veritas autem cuiusque rei est id quod ipsa est. f. 118 v., 1. 30
From: Joseph Thomas Muckle - Isaac Israeli's definition of truth - Archives d'Histoire Doctrinale et Littéraire du Moyen Age 8, (1933) pp. 5-8