Nomos—Law, [43]

Oath, [120]

Objective and subjective truths, [3]

Œnomaos of Gadara, [403]

Onias the Saint, [165], [268], [273]

Ontological proof

See [God's existence]

Optimism, [132], [179], [251]

Order, Moral, of the world, [167]

Orientalism, [470] f.