But though this basis of belief was sufficient for them, yet, as the primary mission of the Christian was to "go, disciple all nations," they were soon brought, in their endeavors to fulfil this command, into contact with those who not only denied the authority of their Teacher, but who were sceptical about the very fundamentals of religious belief. For the sake of these, then, and occasionally for the further confirmation of the faith of believers, and for purposes of illustration, the patristic writers return again to the discussion of those elements of belief for which they themselves felt no need, and hence we have in their works a rather frequent reference to the various forms of the theistic argument; but one which is evidently only incidental to their main course of thought, and which is brought in merely in accommodation to the needs of their readers. The ordinary arguments to prove the existence of God were not at all an essential, or even prominent, feature of early Christian Theology. And because of this secondary and incidental position of these arguments, they were never, as we shall see, given definite, conventional shape in the patristic use of them, nor were the various forms of the argument differentiated; but they were used in what we may call a mixed form, a combination of two or more different forms being put forth as one composite whole. Besides these general influences which shaped the patristic treatment of the theistic arguments, we should notice certain fundamental and characteristic principles assumed by the Fathers, or by most of them, which have their bearing on our subject.