BY common consent the Against Praxeas of Tertullian is one of its author’s most important works. Like many other writings which have sprung out of controversy, it possesses a positive and historic significance also, as the earliest surviving formal statement of the doctrine of the Trinity. It is true that the argument, at least so far as it is based on passages from the Greek version of the Old Testament, or on a Latin translation of that Greek, is not so convincing to the modern student