"There is naturally present in all men the desire to know the causes of whatever things are observed. Hence, because of wondering about things that were seen but whose causes were hidden, men first began to think philosophically; when they found the cause, they were satisfied. But the search did not stop until it reached the first cause, for "then do we think that we know perfectly, when we know the first cause." Therefore, man naturally desires, as his ultimate end, to know the first cause. But the first cause of all things is God. Therefore, the ultimate end of man is to know God."