Reference to psychological fact is what one misses in the records of the old controversies. The disputes read as if they were about shadows. No doubt that was often the case. Catholics and non-Catholics were often agreed as to the substance of belief, while owing to their devotion to words and formulae the agreement went unrecognised. Had the disputants made clear to themselves and to each other what they meant by their abstract terms, had they translated them into their concrete psychological equivalents, heresy and schism would have been less frequent. It was, however, almost impossible for them to do so, because in their day theology was far more highly developed than psychology. Systematic observation of the workings of spirit was almost unknown. There existed no science of psychology as we know it. No clear notions attached to the terms "person" and "nature." They represented abstractions necessary to discursive reason rather than concrete psychic facts. All parties shared this defect. Among catholics and Nestorians as well as among monophysites knowledge of the constituents of human nature was of the most rudimentary character. The catholic party, however, by keeping close to the facts recorded in the gospels, achieved a Christological formula that is psychologically intelligible; while the heretical parties were led by their preconceived opinions to fashion a Christ, whose features are unrecognisable as God or man, a psychological monstrosity. BERGSON'S THEORIES THROW LIGHT ON CHRISTOLOGY Without claiming finality for the findings of modern psychology, we can consider some results of the science as established. They are sufficiently well established, at any rate, to provide a starting-point for our investigation. In particular the brilliant observations and theories of M. Bergson throw, so it seems to the writer, a flood of light on Christology. We propose to outline the two key doctrines of the Bergsonian psychology and show how they confirm the truth of the orthodox formula and expose the monophysite fallacy. These key doctrines are, first, the interpenetration of psychic states, and, second, the distinction between deep-seated and superficial consciousness. BERGSON'S THEORY OF THE INTERPENETRATION OF PSYCHIC STATES