The Cambridge Platonists’ anti-Calvinism was undergirded by a Platonic epistemology of participation – an epistemology on which the faculty of reason allowed the soul to participate in, and thereby come to know, the nature of God. This epistemology, drawn largely from Plotinus, enabled them to defend and articulate their reasons for rejecting the arbitrary, voluntarist picture of God propagated by their Calvinist contemporaries, and defend their own, rival conception of God as unswervingly committed to communicating his overflowing goodness to all his creatures. The central component of this Platonic epistemology is a high view of human reason as a direct participation in the divine nature, where beauty, goodness and truth are inseparably united. This chapter introduces the Cambridge Platonists’ religious epistemology by highlighting the ways in which they make conformity to God, both through purity of mind and virtuous action, a precondition for knowledge of God, resulting in a distinctive combination of Plotinian epistemology and Puritan spirituality.