Natural inclinations, considered in themselves, are good, that is, not a matter of reproach, and it is not only futile to want to extirpate them but to do so would also be harmful and blameworthy. Rather, let them be tamed and instead of clashing with one another they can be brought into harmony in a wholeness which is called happiness.
--Immanuel Kant, Religion within the Limits of Reason Alone, Book 2 (1793)
Man—every man—is an end in himself, not a means to the ends of others; he must live for his own sake, neither sacrificing himself to others nor sacrificing others to himself; he must work for his rational self-interest, with the achievement of his own happiness as the highest moral purpose of his life.
--Ayn Rand, "Introducing Objectivism" (1962)