Are these things done only in us? Many are done only in us — things that rational beings especially need. But you'll find many things we share with non-rational animals. Do animals understand what happens to them? Not at all. Using something is different from understanding it. God needed non-rational animals to use their impressions of the world. But he needed us to understand how to use our impressions. So it's enough for animals to eat, drink, mate, and do whatever else comes naturally to them. But for us — since God also gave us the ability to think — these basic things aren't enough. Unless we act properly and in an orderly way, following the nature of each situation, we'll never reach our true purpose.
What, then, are these things done in us only? Many, indeed, in us only, of which the rational animal had peculiar need; but you will find many common to us with irrational animals. Do they then understand what is done? By no means. For use is one thing, and understanding is another; God had need of irrational animals to make use of appearances, but of us to understand the use of appearances. It is therefore enough for them to eat and to drink, and to copulate, and to do all the other things which they severally do. But for us, to whom he has given also the intellectual faculty, these things are not sufficient; for unless we act in a proper and orderly manner, and conformably to the nature and constitution of each thing, we shall never attain our true end.