The view that the divine substance is some item common to the three persons is frequently rejected in modern trinitarian thought in favour of the view that the divine substance is properly identical with the Father in a way that it is not identical with the Son or Spirit. I argue that these views cannot safeguard the monarchy of the Father, and that in order to safeguard this latter doctrine, it is necessary to hold that the divine substance is some item common to the three persons. I show how this view does not require that there is any sense in which the divine substance is prior to the divine persons.