Aquinas on Divine Simplicity

The paper corrects misrepresentations of Aquinas's understanding of divine simplicity, argues that the reasons he gives for divine simplicity are persuasive ones, and suggests how Aquinas's account of the Trinity can be used to explain how God can be said to exist necessarily. It gives an account of Aquinas's conception of form and individualised form, and shows how Plantinga's criticism of Aquinas's position on divine simplicity rests on a misunderstanding of Aquinas's notion of form. It describes and makes the case for Aquinas's argument that God must be absolutely simply because he is the uncaused cause of all effects, and any real composition in things constitutes an effect. It shows that Brian Davies is mistaken in claiming that Aquinas does not hold God's existence to be logically necessary. It applies Frege's conception of existence to Aquinas's account of God's simplicity and his psychological analogy for the Trinity, in order to explain how God's existence can coherently be said to be logically necessary.