It should be understood that there is implanted in the soul by nature a faculty of desiring that which is in harmony with its nature, and of maintaining in close union all that belongs essentially to its nature: and this power is called will or θέλησις. For the essence both of existence and of living yearns after activity both as regards mind and sense, and in this it merely longs to realise its own natural and perfect being. And so this definition also is given of this natural will: will is an appetite, both rational and vital, depending only on what is natural. So that will Max. ad Marin. et ad Incert. p. 98. is nothing else than the natural and vital and rational appetite of all things that go to constitute nature, that is, just the simple faculty. For the appetite of creatures without reason, since it is irrational, is not called will.