The origin of our passions, the root and spring of all the rest, the only one which is born with man, which never leaves him as long as he lives, is self-love; this passion is primitive, instinctive, it precedes all the rest, which are in a sense only modifications of it. In this sense, if you like, they are all natural. But most of these modifications are the result of external influences, without which they would never occur, and such modifications, far from being advantageous to us, are harmful. They change the original purpose and work against its end; then it is that man finds himself outside nature and at strife with himself.

Emile, or On Education (1762) - Book IV