Aristotle, Nicomachean Ethics
H. Rackham, Ed.

being loved a passive one; hence affection and the various forms of friendly feeling are naturally found in the more active party to the relationship. [7]

Again, everybody loves a thing more if it has cost him trouble: for instance those who have made money love money more than those who have inherited it. Now to receive a benefit seems to involve no labor, but to confer one is an effort. （This is why mothers love their children more than fathers, because parenthood costs the mother more trouble [and the mother is more certain that the child is her own].¹） This also then would seem to be a characteristic of benefactors. 8.

The question is also raised whether one ought to love oneself or someone else most. We censure those who put themselves first, and ‘lover of self’ is used as a term of reproach. And it is thought that a bad man considers himself in all he does, and the more so the worse he is—so it is a complaint against him for instance that ‘he never does a thing unless you make him’ —whereas a good man acts from a sense of what is noble, and the better he is the more he so acts, and he considers his friend's interest, disregarding his own. [2]

But the facts do not accord with these theories; nor is this surprising.