 Although, for Eriugena, “rational animal” does not completely define human nature, this mirroring of God in man occurs especially in the cognitive domain. Like Maximus, Eriugena argues that God knows that He is (quia est), but not what He is (quid est). God has existential knowledge, but no circumscribing knowledge of His essence, since, as infinite, He is uncircumscribable: