The Essence of Reality

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 the realities having a given identity or intelligible essence in and through all the changes that it undergoes. We identify the essence of a natural reality based upon its natural form. If you were scientists and you sent your assistant into the biology lab to get the mice and he came back with the orangutan, you would wonder about his sanity.