While the other lectures at this Conference have explored the deeper theological issues raised by the Nicene Creed, the aims of this lecture are primarily historical. I should like to tell you something of the origins of the creed, and how it came to be adopted — or at least used — at the First Council of Constantinople in October 381. Theology will of course make its appearance, for it was in the context of the acrimonious theological debates of the fourth century that the creed emerged; and there is a profound sense in which, as I shall very briefly suggest, its adoption marked a significant turning-point. But my treatment of the theological background, and of the theological revolution of which it was the token, will remain historical.