"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 1011 b).
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 () 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
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, corresponde n tia 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)" (p. 5)
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." (pp. 6-7)
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." (pp.
(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