  However that may be, Aristotle’s conception of thinking implicates him in supposing that thought involves grasping the structural features of the objects of thought. To take an initially favorable case, when thinking that tree frogs are oviparous, S will be in a psychic state whose internal structural states are, among other things, one in form with tree frogs. Since S’s soul does not become a tree frog when thinking of tree frogs (De Anima iii 8, 431b24–30), this form of isomorphism cannot be mere instantiation of the form being a tree frog. Rather, S’s mind will evidently be one in form with the tree frog, to revert to our earlier analogy, in something like the way a blueprint and the house of which it is the blueprint are one in form. There must be a determinate and expressible structural isomorphism, even though one could not say that the blueprint realizes the form of the house. Houses are, after all, necessarily three-dimensional.