A philosophical understanding of race begins with the canon. In the Republic, Socrates proposed telling youth that they are born with traits of leaders, soldiers, or workers. Aristotle accepted slavery as natural and described enslaved Asians as lacking in spirit. Saint Paul and Saint Aquinas accepted slavery in this world. John Locke reserved slavery for captives taken in a just war. Hume said that nonwhites, especially Africans, are inferior to whites. Kant posited racial essences as determining moral worth and intellectual capabilities. Hegel posited geography as determining human difference and called Africa "the land of childhood." Nietzsche assumed racial hierarchy and proposed a new blonde ruling race. John Stuart Mill reserved liberty for mature individuals and societies advanced in civilization.