The Christian doctrine of the Trinity holds that God is one God, but three coeternal consubstantial persons or hypostases—the Father, the Son, and the Holy Spirit—as "one God in three Divine persons". The three persons are distinct, yet are one "substance, essence or nature" (homoousios). In this context, a "nature" is what one is, whereas a "person" is who one is. The subset of Christianity that accepts this doctrine is collectively known as trinitarianism, while the subset that doesn't is referred to as nontrinitarian. Trinitarianism contrasts with positions such as Binitarianism and Monarchianism, of which Modalistic Monarchianism and Unitarianism are subsets.