Classicly

Reproduction or accumulation of identities similar to self is a common law of animal and vegetable matter; and the disposition to reproduce in all well-formed and healthy subjects is as powerful as hunger, or thirst, or the desire of self-preservation. It is a passion not criminal in the indulgence, but criminality attaches where the indulgence is withheld; because health, and even life, is endangered. It is not an artificial passion, such as a craving to exhibit the distinctions of society; but a natural passion, which we hold in common with every other animal. It grows with our growth, and is strengthened with our strength.