"To believe rightly the incarnation of our Lord Jesus Christ" is an ideal that the thoughtful Christian strives to attain. He expects to find the solution of high moral and speculative problems in that union of divine and human. The right faith is not easily reached. It is an elusive prize. There are conditions moral and intellectual attaching to its possession. The moral conditions may take a lifetime to fulfil. Even on its intellectual side faith is a long process. No sudden mental grasp of the whole truth can be attained. It dawns on the mind gradually. The discipline of faith in the incarnation consists in a gradual and laborious advance from stage to stage. The various stages are half-truths or inadequate conceptions of Christ. They are objectified in the Christological heresies. These heresies arrange themselves in a sequence so strict and so logical that one could almost say that they are deducible _a priori_ from the concept "divine-human." Certainly the subjective fancies of the heresiarchs do not provide the whole account. There is something of the universal in these heresies. They are in the main current of religious thought. As the chief historic systems of philosophy repeat themselves in each generation and in the intellectual development of individual thinkers, so do the Christological heresies recur. There is considerable truth in Hegel's contentions that the development of a man's mind is one with that of the general consciousness, that the individual reason is a miniature of the universal reason, that in fact the history of a philosopher's thinking is an abstract of the history of philosophy. The same holds good in the field of religious thought. Without much artificiality, without forcing the facts, a rational scheme of the Christological heresies might be drawn up. They might be pictorially represented as the rungs of a ladder, which the truth-seeking mind scales rung by rung, pausing at the lower phases of Christological thought, and then resuming the ascent till the highest truth is attained. The instrument of thought is much the same in all centuries; the objects of thought vary very little; so it is intelligible that the products of speculative and religious thought should remain the same to-day as in the fifth century.