Early in the fourth century Constantine made Christianity the religion of the Roman Empire, and at once had reason to regret his having done so; for now not only the Church but the state was convulsed by controversies about the Holy Trinity. These controversies raged for over two hundred years, after which the bishops found new intellectual outlets, if not more rational ones, for their animosities. But Trinitarian trouble was not dead, only sleeping. The Great Schism of the eleventh and twelfth centuries, which split the Western from the Eastern Church, took place, on its theological side, over a question concerning the Trinity. This was, of course, that most famous of all theological questions, the question of the procession of the Holy Ghost, or of the filioque. The Orthodox theory was that the Holy Ghost proceeds from the Father alone. The Western bishops, however, were equally adamant that the Holy Ghost proceeds from the Father filioque - 'and the Son'.
It is obvious enough that these two opinions could not both be right, though both could be wrong. It is equally obvious that both opinions are wrong, or at least, that they each have got something dreadfully wrong with them, and the same thing. They both have some fatal congenital defect, whatever the exact nature of this defect may be. And it is equally obvious too, that this defect will also be shared by any other answer to the question, what or whom the Holy Ghost proceeds from. It does not matter much how you answer this question: something has already gone fatally wrong with your thoughts, once you find yourself so much as asking it.