The next error that the Church had to face concerning the person of Christ was that of Apollinarianism. This system denied the completeness of His human nature. It acknowledged His true Deity, and also that He possessed a real body and a soul which would continue after death; but it denied that He had a truly human mind, i.e., a reasoning mind that reached conclusions through mental processes as do ours.

It asserted in effect that He was simply God masquerading in human flesh, and that ignorance, weakness, obedience, worship, suffering, etc., were to be predicated of the Logos, that is, of the Deity or Divine nature as such. If, by way of comparison, we can imagine a man\’s mind implanted in the body of a lion and the lion thereafter governed not by lion or animal psychology but by a human mind we shall have something analogous to what the Apollinarian system set forth concerning the incarnation of Christ. Apollinarius was a tricotomist, and his system was based on the assumption that there were three elements in man\’s nature: a material body, an immortal soul, and a reasoning mind.

We believe, however, that man is composed of only two elements, body and soul, and that the mind with which man reasons in this life is the same as the soul or spirit which lives on after death. Hence it is evident that, reduced to dicotomist terms, Apollinarianism granted Christ a human body but not a complete human soul.

But if Christ was to have a real incarnation it was necessary that He add to His divine nature not merely a human body but also a human mind or soul; for humanity consists not merely in the possession of a body but of a body and soul. Apollinarianism was plainly an inconsistent explanation of the person of Christ, and it was condemned by the Council of Constantinople in the year 381.