William Hasker reviews the evidence concerning fourth-century pro-Nicene trinitarianism in the light of recent developments in the scholarship on this period, arguing for particular interpretations of crucial concepts. He then reviews and criticises recent work on the issue of the divine three-in-oneness, including systematic theologians such as Barth, Rahner, Moltmann, and Zizioulas, and analytic philosophers of religion such as Leftow, van Inwagen, Craig, and Swinburne.