the other: and it is in this matter of their common consent that they both commit suicide. Every process in the physical sphere must be supposed to have its equations satisfied within that sphere: else the doctrine of the conservation of energy would be contravened, and thus the causation contemplated could no longer be contemplated as physical. Similarly, every process in the mental sphere must be supposed to have its equations satisfied within that sphere: else the causation contemplated could no longer be contemplated as mental: some of the equations must be supposed not to have been satisfied within the mental sphere, but to have been carried over into the physical sphere--thus to have either created or destroyed certain quantities of energy within that sphere, and thus, also, to have introduced elements of endless confusion into the otherwise orderly system of Nature. From this vice of radical contradiction, to which both the dualistic theories are committed, the monistic theory is free. Moreover, as we shall immediately find, it is free to combine the elements of truth which severally belong to both the other theories. These other theories are each concerned with what they see upon different sides of the same shield. The facts which they severally receive they severally report, and their reports appear to contradict each other. But truth can never be really in contradiction with other truth; and it is reserved for Monism, by taking a simultaneous view of both sides, to reconcile the previously apparent contradictions. For these and other reasons, which will unfold themselves as we proceed, I fully agree with the late Professor Clifford where he says of this theory--'It is not merely a speculation, but is a result to which all the greatest minds that have studied this question (the relation between body and mind) in the right way have gradually been approximating for a long time.' This theory is, as we have already seen, that mental phenomena and physical phenomena, although apparently diverse, are really identical.