Materialists, as already observed, are fond of saying that the evidence of causation from neurosis to psychosis is as good as such evidence can be proved to be in any other case. Now, quite apart from the general considerations just adduced to show that from the peculiar nature of this case there can here be no such evidence at all--quite apart from this, and treating the problem on the lower ground of the supposed analogy, it may be clearly shown that the statement is untrue. For a little thought will show that in point of fact the only resemblance between this supposed case of causation and all other cases of recognized causation, consists in the invariability of the correlation between cerebral processes and mental processes; in all other points the analogy fails. For in all cases of recognized causation there is a perceived _connexion_ between the cause and the effect; the antecedents are physical, and the consequents are physical. But in the case before us there is no perceived, or even conceivable, connexion between the cause and the effect; for the causes are supposed to be physical and the effects mental. And the antithesis thus posited is alone sufficient to separate _toto coelo_ the case of causation supposed from that of all cases of causation recognized. From the singularly clear and well-balanced statement of this subject given by Professor Allman in his Presidential Address before the British Association, I may here fitly quote the following:-- 'If we could see any analogy between thought and any one of the admitted phenomena of matter, we should be justified in the first of these conclusions (i. e. that of Materialism) as the simplest, and as affording a hypothesis most in accordance with the comprehensiveness of natural laws; but between thought and the physical phenomena of matter there is not only no analogy, but no conceivable analogy; and the obvious and continuous path which we have hitherto followed up in our reasonings from the phenomena of lifeless matter through those of living matter here comes suddenly to an end. The chasm between unconscious life and thought is deep and impassable, and no transitional phenomena can be found by which, as by a bridge, we may span it over[6].' And, not unduly to multiply quotations, I shall only adduce one more from another of the few eminent men of science who have seen their way clearly in this matter, and have expressed what they have seen in language as clear as their vision. Professor Tyndall writes:--