 All warfare was illegal and unjust and only through the papal mandate of peacefully bringing Christianity to heathen peoples could "Just Titles" be acquired.As a part of Las Casas's defense by offense, he had to argue against Juan Ginés de Sepúlveda.Sepúlveda was a doctor of theology and law who, in his book "Democrates Alter, sive de justis causis apud Indos" (Another Democrates /or A New Democrates, or on the Just Causes of War against the Indians) had argued that some native peoples were incapable of ruling themselves and should be pacified forcefully.