 William Hasker (2013b) has constructed what is arguably the most developed three-self theory of the Trinity. As with Swinburne, his thoughts have developed over decades (Tuggy 2013b), but this entry will focus on his recent publications. For Hasker, following Plantinga, the Persons of the Trinity are “distinct centers of knowledge, will, love, and action…persons in some full sense of the term” (22; cf. Chapter 24). Hasker argues that such a view is widespread in ancient sources, including Gregory of Nyssa and Augustine (Chapters 4–5, 9). While we can’t reasonably retain the ancient doctrine of divine simplicity (Chapter 7, 2016, 2018a, 7–8, 18–9), we ought to uphold as many of the traditional claims as possible, for we should assume divine guidance of theological development, even though “the Church’s doctrine of the Trinity is not as such to be found in the New Testament” (8). The “fathers” of the late fourth century should be seen as “the giants on whose shoulders we need to stand” (10). In the second part of his book (Chapters 11–20) Hasker interacts with a number of Trinity theories, attempting to salvage whatever is correct in them for use in his own three-self theory; he incorporates ideas particularly from Leftow, Craig, Rea, and Swinburne.