Two Catholic moralists of Spain's "siglo de oro," Francisco de Vitoria (1483-1546) and Domingo de Soto (1494-1560), examined the condition of the Indians of the New World. Using the theological system of Saint Thomas Aquinas (1225-1274), they attacked the excesses of the "conquistadores" but concluded that slavery was justifiable under some circumstances. This study compares and contrasts their adapted notion of the critical concepts of -right- and -dominion- with the original perspective of Aquinas."