Short Essay: Thomas’s doctrine of “theological truth” or the “truth of things.”
In the Summa, after his discussion of the divine ideas, the very next question entertained by St. Thomas concerns the subject of truth, with the very first article asking “whether truth is only in the intellect?” (ST 1.16.1). Thomas’s reply is that, although truth is principally in, being first and foremost a property of, the intellect, because truth establishes a relation between the intellect and the thing known—“the true [existing] in the intellect in so far as it is conformed to the thing understood”—there is an important sense in which “the aspect of the true must pass from the intellect to the thing understood, so that also the thing understood is said to be true in so far as it has some relation to the intellect.” In other words, when an intellect becomes truthfully related to a thing, the thing itself is not left unaffected, but reciprocates by likewise entering into a truthful relationship with the knowing intellect. And even when a thing is not actively being known by any intellect, it still exists in a state of potentiality for being known, a potentiality that is no mere accidental feature of, but is constitutive of, the thing in its very being. As Josef Pieper has aptly described Thomas’s teaching concerning truth’s status as a “transcendental” property of all being,
[e]very being, as being, stands in relation to a knowing mind. This relational orientation toward a knowing mind represents the same ontological reality as the very being of a thing…. With all “being” thus related to a knowing mind, we further state that this relationship is actualized in the process of mental perception or intellection. “The mind’s act of intellection itself constitutes and completes that relation of ‘conformity’ which is the nature of truth.”
Although a thing always exists in this state of “relational orientation toward a knowing mind,” or rather precisely on account of it, there is a very real sense in which it is only by being known that a thing is finally allowed to reach its completion or perfection. By knowing things and thus realizing their potential for being known, the human intellect gives things the opportunity to be what they truly are, providing them, so to speak, with the stage upon which they might enact their foreordained part. As Catherine Pickstock has observed, there is thus an almost redemptive dimension to the intellect’s role in actualizing the truth potential of things, their innate capacity, that is, for being known:
one must think of knowing-a-thing as an act of generosity, or salvific compensation for the exclusivity and discreteness of things. … It is a corrective or remedy, according to Aquinas in De Veritate, for the isolation of substantive beings… [T]he very notion of a “thing itself” is radically otherwise, for it is only “itself” in its being conformed to the intellect of the knower… The thing-itself is only itself by being assimilated to the knower, and by its form entering into the mind of the knower.
Here Maritain is also worth mentioning again, as he connects this Thomistic sense of the radical co-belongingness of the human mind and things with the reason why human beings can have an aesthetic experience of the natural world: “Take the objects of aesthetic delight which are the most completely remote from any impact of humanity… Everywhere in reality, man is there, under cover. Man’s measure is present, though hidden. All these nonhuman things return to man a quality of the human mind which is concealed in them…”
Yet the primary basis for Thomas for both the knowing intellect’s truthful orientation towards things, and the truthful orientation of things towards the knowing intellect, is that each are ultimately oriented towards the divine intellect in which both intellect and things have their origin. Because all things owe their existence to the divine intellect, making them “essentially” related to it, Thomas concludes that “[i]n the same way natural things are said to be true in so far as they express the likeness of the species that are in the divine mind. For a stone is called true, because it expresses the nature proper to a stone, according to the preconception in the divine intellect” (ST 1.16.1). In short, because things have been created and patterned after their corresponding idea or exemplar in the divine mind, things exist in this state of continuous conformity to that mind, the consequence of which is that things are by nature not alien or indifferent to, but fundamentally akin and so intelligible to the knowing mind. As Pieper again elaborates on this relationship, “things can be known by us because God has creatively thought them; as creatively thought by God, things have not only their own nature (‘for themselves alone’); but as creatively thought by God, things have also a reality ‘for us.’”
 For a history of the doctrine of the “truth of things,” see Pieper, The Truth of All Things. Pieper traces the doctrine as far back as the pre-Socratic philosopher Pythagoras, through Aquinas, and forward to its dissolution in modernity. On Thomas’s doctrine of the truth of things in particular, see also Phelan, “Verum Sequitur Esse Rerum” and Pickstock, “Truth and Correspondence.”
 “[I]ta, cum verum sit in intellectu secundum quod conformatur rei intellectae, necesse est quod ratio veri ab intellectu ad rem intellectam derivetur, ut res etiam intellecta vera dicatur, secundum quod habet aliquem ordinem ad intellectum.”
 As Catherine Pickstock explains the dynamic reciprocity involved in Thomas’s theory of truth, the intellectual apprehension of truth “is not an indifferent speculation; it is rather a beautiful ratio which is instantiated between things and the mind which leaves neither things nor mind unchanged.… If, for example, one were to know a willow tree overhanging the Cherwell, our knowing of it would be just as much an event in the life of the form ‘tree’ as the tree in its willowness and in its growing.” Pickstock, “Truth and Correspondence,” 9.
 Pieper, The Truth of All Things, 35, citing St. Thomas’s commentary on Peter Lombard’s Book of Sentences: “In ipsa operatione intellectus … completur relatio adaequationis, in qua consistit ratio veritatis” (Sent. 22.214.171.124).
 Pickstock, “Truth and Correspondence,” 9 (emphasis original). As Maritain has similarly written, “object and objectivity are the very life and salvation of the intellect.” Maritain, Existence and the Existent, 23.
 Maritain, Creative Intuition, 6.
 “Et similiter res naturales dicuntur esse verae, secundum quod assequuntur similitudinem specierum quae sunt in mente divina: dicitur enim verus lapis, qui assequitur propriam lapidis naturam, secundum praeconceptionem intellectus divini.”
 Pieper, The Silence of St. Thomas, 55.