God's Will

To exist is actually to possess our own natural form; to know actually to possess the form of what we know. When things haven't got their natural form and perfections they seek them and do not rest till they have them; and in things lacking awareness we call this tendency towards their natural good their natural desire. In the same way things with understanding have a natural tendency to seek whatever they understand as good, not resting till they possess it; and this tendency we call will. So anything that has understanding has will, just as anything that has sense-perception has animal desire. We call will a desire or an appetite, through it doesn't only desire what it doesn't have but also loves and takes delight in what it does have. And this is how will exists in God, who eternally possesses the good which delights his will, since it is nothing other than his substance.

Summa Theologiae
A Concise Translation
Edited By Timothy McDermott