364 E. E. c. JONES : subject experiencing is entirely ignored" (ii., 10, 11). Sup- pose we take it for the present that when we speak of the parallelism of physical and psychical series, by psychical is meant my experience not as it is for myself but as it is for the psychologist who is studying my brain and my organs of sense and movement. Even then, when we come to ask what is meant by the parallelism of the two series, their absolute disparateness seems to exclude entirely that serial correspondence which is what is understood to be meant by parallel. It is not necessary to follow Dr. Ward's account of the unsuccessful attempts to introduce a substantial unity where we have not succeeded in getting any qualitative unity (ii., 15-21) which are made in Clifford's theory of Mind-Stuff (which turns out to be only a crude form of materialistic Monism under a fresh name) and in the Two- Aspects Theory which fails " to indicate the unity to which [the aspects] belong and to show that they have such congruence as befits complementary sides or aspects of the same thing ". These endeavours breaking down, we go on to the Conscious Automaton Theory, according to which there is invariable concomitance between the series, but no causal interaction. The theory of Psycho-physical Parallelism is represented by its supporters as a strict inference from facts (ii., 6) and no mere speculation, but Dr. Ward undertakes to show that both these assertions are inaccurate, and that the basis of the theory is that Cartesian dualism which he regards as speculation of the most questionable kind. He shows that the 'Conscious Automaton' doctrine has defects which oblige us to doubt its implicit assumptions, and then (in Part iv.) proceeds to expose the shortcomings of that Dualism which the theory of Psycho-physical Parallelism presupposes. In Conscious Automatism the dualism between the psychi- cal and physical series is accepted as complete, and their concomitance as invariable but not causal there is co- existence in space and time but no interaction. But the self-contained completeness of the psychical series is threatened by Sensation, and that of the physical series by Life (ii., 25, etc.). Here Dr. Ward points out that if the two series are really independent and separate, each going along by itself, both parallelism and interaction are alike inconceivable, and if they are really members of one whole, they cannot be severed from each other and yet be the same as they were before. "Constant parallelism plus absolute separation is logically .so unstable a combination that of