Reply Obj. 2: Things do not deceive by their own nature, but by accident. For they give occasion to falsity, by the likeness they bear to things which they actually are not.
Reply Obj. 3: Things are said to be false, not as compared with the divine intellect, in which case they would be false simply, but as compared with our intellect; and thus they are false only relatively.
To the argument which is urged on the contrary, likeness or defective representation does not involve the idea of falsity except in so far as it gives occasion to false opinion. Hence a thing is not always said to be false, because it resembles another thing; but only when the resemblance is such as naturally to produce a false opinion, not in any one case, but in the majority of instances. _______________________
SECOND ARTICLE [I, Q. 17, Art. 2]
Whether There Is Falsity in the Senses?
Objection 1: It seems that falsity is not in the senses. For Augustine says (De Vera Relig. 33): "If all the bodily senses report as they are affected, I do not know what more we can require from them." Thus it seems that we are not deceived by the senses; and therefore that falsity is not in them.
Obj. 2: Further, the Philosopher says (Metaph. iv, 24) that falsity is not proper to the senses, but to the imagination.
Obj. 3: Further, in non-complex things there is neither true nor false, but in complex things only. But affirmation and negation do not belong to the senses. Therefore in the senses there is no falsity.
On the contrary, Augustine says (Soliloq. ii, 6), "It appears that the senses entrap us into error by their deceptive similitudes."
I answer that, Falsity is not to be sought in the senses except as truth is in them. Now truth is not in them in such a way as that the senses know truth, but in so far as they apprehend sensible things truly, as said above (Q. 16, A. 2), and this takes place through the senses apprehending things as they are, and hence it happens that falsity exists in the senses through their apprehending or judging things to be otherwise than they really are.