According to the standard Thomistic account, God can be known both by nature and revelation. The first is the terrain of metaphysics, which knows God as the cause of his created effects. The second is theology, which knows God through the words in which he has revealed himself. Often neglected, however, is a third way that Aquinas maintains God can be known. Affective knowledge, which proceeds by way of intuition, experience, and union, is fundamental to Aquinas's theological method. The central claim of this book is that, for Aquinas, the new life of grace given in baptism also entails a new affective, connatural knowledge of the things of God. This “loving knowledge,” which finds its consummation in beatific knowing, reverberates throughout Aquinas's theological epistemology, underwriting his account of the doctrine of gifts of the Holy Spirit, divine indwelling, the spiritual senses, and theological contemplation.