This seems to be wrong, indeed. For authorities claim unanimously that Aristotle was an empiricist who opposed Plato’s rationalism, and that Aquinas followed his viewpoint. As an evidence they quote Aristotle’s famous maxim about the human mind as an empty board at which sensory experiences write down their records. This is to mean: the human mind understands nothing that has not been first perceived by senses. This view happens to be called genetic empiricism.
However, at the same time, both of them assert the existence of truths which are necessary, hence irrefutable by experience, and ascribe them a fundamental role in forming knowledge — as first principles of logic, mathematics, metaphysics. It looks as if they lacked the awareness of contradiction between that claim and their genetic empiricism (what many centuries later was acutely discussed by David Hume).
They may have believed that what prevents inconsistency it is the conception of intellectus agens (the active intellect) which performs the job of extracting general and abstract ideas from the concrete stuff of sense data. Psychologically, it is really the case that the mind makes such generalizations; that ability may be attributed to what one calls active intellect. However, such inductive generalizations too frequently prove to be false. There is no logical warrant to grant such inferences the rank of truths being necessary, and thereby secure against any empirical counterexamples.
In what follows, I focus my argument on St.Thomas’ views as, presumably, more remote from empiricism than those of Aristotle (a more personal reason is that I better understand Latin than Greek). At the very start of his Summa Theologiae (Question One, 2nd Article) he puts the following statements. Physics is a science which logically follows from geometry, while the latter consists of principles known to mind owing to the natural light – lumen naturale.
This concept of natural light (more Platonian, after Augustine, than Aristotelian) plays a key role in Aquinas’ epistemology. Let us read a passage from the same work which runs as folows (first I quote the Latin original so that readers may check my interpretation).
Anima humana omnia cognoscat in rationibus aeternis; per quarum participationem omnia cognoscimus: ipsum enim lumen intelectuale, quod est in nobis, nihil est aliud, quam quaedam participata similitudo luminis increati, in quo continentur rationes aeterne. (S.Th., pars I, q.84, a.5).
Here is a translation. “The human soul perceives all things in eternal principles by participating in them. The light of natural reason we have within us is nothing else than a certain participated likeness of the uncreated light in which are contained eternal principles.” (The phrase “lumen intellectuale” may be replaced, in Aquinas’ own language by “light of natural reason”, which is more useful for the present discussion.)
Let us compare this notion with Descartes’ conception of the light of natural reason. For the lack of his original definition, let us take advantage of the following conjectural interpretation.
“Descartes dwells on the notion of natural light (lumen naturalis, or lumiere naturelle), intuition. For him, it does not make some exceptions to the laws of nature. Rather, it is part of nature. Although Descartes never gives clarification to this concept, he supposed, God creating the universe, had a certain plan that is fully embodied in the universe as a whole and in part – in its separate parts. This plan is also embedded in the human mind, so that the mind can know nature, and even have a priori knowledge about nature, because the mind and objectively existing nature are reflections of the same divine plan.”
The doctrine of Descartes has created a firm paradigm of rationalism. Therefore, were Aquinas’ views in accordance with Descartes’ approach to the light of reason, this would evidence the rationalistic core of Aquinas’ thought. Is it truly the case?
In the quest for answer, I suggest an excursion into the realm of biological a priori as a case of programming in Nature. Let us compare the whole world to a colony of ants, and an individual brain to the brain of an ant specimen. There has to be something like a software – a plan to organize the whole colony’s activity, while some microscopic subprograms would be distributed among particular ants, corresponding to the tasks to be performed by them. Such a whole may resemble what computer scientists call distributed computing. If we agree to apply the emphatic word “lumen” to any set of instructions which throw light on the question “how to do that?”, then we approximate the nature of participation of those microscopic procedures in a giant global program.
In the interpretation regarding Descartes, as quoted above, one speaks of “a certain plan which — according to Descartes — gets embodied in the universe as a whole”, and gets distributed into some elements of the universe. Any portion of such a plan embedded in a mind would be this mind’s aprioric konowledge. So far as regards Descartes.
As to Aquinas, he speaks of participating of natural reason in eternal principles, and its acquiring from that source some pieces of knowledge, independently of any sense data. This is certainly an argument for the existence of aprioric knowledge. Aquinas, like Aristotle, and unlike Plato, does not claim that this has to be a ready knowledge. It may be something like an ability, or a set of rules followed by the mind to attain knowledge, but nevertheless there is something being a priori (whose special case may be instincts of animals).
And this is why there are reasons to acknowledge Aquinas as a genuine rationalist in spite of all the distance, shared with Aristotle, which he held towards Plato.
What do you, Benevolent Reader, think about that? If you are not happy with the argument of this post, have a look at its sequel titled “Is it the case that there has arisen computational rationalism?” Any comments of yours will be welcome.