What Is the Natural Form?

For Aquinas, the form is first an intrinsic principle of determination that gives stable identity to a given reality through time. Second it is the cause of realities having a given identity or intelligible essence in and through all the changes that it undergoes. It is also third the principle of internal organization of the material parts of a given reality so that those parts can be identified always only as part of a given kind of reality. The form is fourthly the essential source of stable properties and fifthly the foundation for teleological outcomes.