On the contrary, The intelligible species is to the intellect what the sensible image is to the sense. But the sensible image is not what is perceived, but rather that by which sense perceives. Therefore the intelligible species is not what is actually understood, but that by which the intellect understands.
I answer that, Some have asserted that our intellectual faculties know only the impression made on them; as, for example, that sense is cognizant only of the impression made on its own organ. According to this theory, the intellect understands only its own impression, namely, the intelligible species which it has received, so that this species is what is understood.
This is, however, manifestly false for two reasons. First, because the things we understand are the objects of science; therefore if what we understand is merely the intelligible species in the soul, it would follow that every science would not be concerned with objects outside the soul, but only with the intelligible species within the soul; thus, according to the teaching of the Platonists all science is about ideas, which they held to be actually understood [Question Eighty-four, Article One: Whether the Soul Knows Bodies Through the Intellect?]. Secondly, it is untrue, because it would lead to the opinion of the ancients who maintained that ‘whatever seems, is true’ [Aristotle, Metaph. III. 5], and that consequently contradictories are true simultaneously. For if the faculty knows its own impression only, it can judge of that only. Now a thing seems according to the impression made on the cognitive faculty. Consequently the cognitive faculty will always judge of its own impression as such; and so every judgment will be true: for instance, if taste perceived only its own impression, when anyone with a healthy taste perceives that honey is sweet, he would judge truly; and if anyone with a corrupt taste perceives that honey is bitter, this would be equally true; for each would judge according to the impression on his taste. Thus every opinion would be equally true; in fact, every sort of apprehension.
Therefore it must be said that the intelligible species is related to the intellect as that by which it understands: which is proved thus. There is a twofold action (Metaph. IX, Did. VIII, 8), one which remains in the agent; for instance, to see and to understand; and another which passes into an external object; for instance, to heat and to cut; and each of these actions proceeds in virtue of some form. And as the form from which proceeds an act tending to something external is the likeness of the object of the action, as heat in the heater is a likeness of the thing heated; so the form from which proceeds an action remaining in the agent is the likeness of the object. Hence that by which the sight sees is the likeness of the visible thing; and the likeness of the thing understood, that is, the intelligible species, is the form by which the intellect understands.
But since the intellect reflects upon itself, by such reflection it understands both its own act of intelligence, and the species by which it understands. Thus the intelligible species is that which is understood secondarily; but that which is primarily understood is the object, of which the species is the likeness. This also appears from the opinion of the ancient philosophers, who said that ‘like is known by like.’ For they said that the soul knows the earth outside itself, by the earth within itself; and so of the rest. If, therefore, we take the species of the earth instead of the earth, according to Aristotle (De Anima iii, 8), who says ‘that a stone is not in the soul, but only the likeness of the stone’; it follows that the soul knows external things by means of its intelligible species.
This is a crucial passage for understanding Aquinas’s views. Consider two positions on the relation between mind and the external world:
Direct realism In perception and thought, the mind is directly connected to the things it perceives and thinks about, and these are (typically) really existing external objects.
Indirect realism (‘representationalism’) In perception and thought, the mind is only indirectly connected to the things it perceives and thinks about; what it immediately perceives or thinks about is only a mental entity, which in turn represents the thing in the world.
- Which view does Aquinas endorse? Why?