The two primitive forms of doctrinal error, to which the Church, even in apostolic days, was exposed, were docetism and ebionitism. These are the elemental heresies. All the later Christological heresies are refinements of one or other of these two. They constitute the extremes of Christological thought: between them runs the _via media_ of orthodoxy. Each of the two sees but one aspect of the two-fold life of Christ. Docetism lays an exclusive emphasis on His real divinity, ebionitism on His real humanity. Each mistakes a half truth for a whole truth. The docetists denied that Jesus Christ had come in the flesh. His body, they taught, was an apparition. He ate and drank, but the physical frame received no sustenance. He appeared to suffer, but felt no pain. The reality behind the semblance was the divine spirit-being, who conjured up the illusion in order to elevate the thoughts of mankind. This docetic theory commended itself to many of the Greek Christians. They were familiar with the notion of "the gods coming down to them in the likeness of men." Greek mythology abounds in instances of docetic incarnations. The gods of the popular religion constantly assumed visible form during their temporary manifestations. The ebionites threatened the Faith from the opposite quarter. They taught that Christ was real man and only man. According to them, the whole value of His life and work lay in His moral teaching and His noble example; there is no mystery, no contact of divine and human in Christ; what He attained, we all may attain. The ebionites were recruited from the Jewish element in the Church. The rigid monotheism of the Jews made it hard for them to conceive an intermediary between God and man; they were naturally disposed to embrace a humanistic explanation of Christ. Docetism was elaborated by Valentinus, Manes and other gnostics and adopted into their systems, while ebionitism provided the basis for the Christologies of Paul of Samosata, of the Photinians and Adoptionists. In contact with these heresies orthodox beliefs, originally fluid, gradually hardened. The dogma "Christus deus et homo" had from the beginning been held in the Church. Its full implications were not realised and formulated until the conflict with error came. The controversies of the third and fourth centuries threw into bold relief the unity of the person and the perfection of the divinity and of the humanity. THE PROBLEM OF THE HYPOSTATIC UNION The manner of the hypostatic union then became an urgent problem. The Church of the fifth century was called upon to attempt a solution. Any reading of the Gospels compelled the recognition of divine and human elements in Christ; but speculative theology found it difficult to reconcile that fact with the equally important fact of the unity of person.