"If it is contrary to the doctrine of the persistence of physical energy to suppose a transition from the one province to the other, and if, nevertheless, the two provinces exist in our experience as distinct, then the two sets of phenomena must be unfolded simultaneously, each according to its laws, so that for every phenomenon in the world of consciousness there is a corresponding phenomenon in the world of matter, and conversely (so far as there is reason to suppose that conscious life is correlated with material phenomena). The parallels already drawn point directly to such a relation; it would be an amazing accident, if, while the characteristic marks repeated themselves in this way, there were not at the foundation an inner connection. Both the _parallelism_ and the _proportionality_ between the activity of consciousness and cerebral activity point to an _identity_ at bottom. The difference which remains in spite of the points of agreement compels us to suppose that one and the same principle has found its expression in a double form. We have no right to take mind and body for two beings or substances in reciprocal interaction. We are, on the contrary, impelled to conceive the material interaction between the elements composing the brain and nervous system _as an outer form of the inner ideal unity of consciousness_. What we in our inner experience become conscious of as thought, feeling, and resolution, is thus represented in the material world by certain material processes of the brain, which as such are subject to the law of the persistence of energy, although this law cannot be applied to the relation between cerebral and conscious processes. It is as though the same thing were said in two languages." Some monists are in the habit of speaking of the one Being to which they refer phenomena of all sorts as the "Absolute." The word is a vague one, and means very different things in different philosophies. It has been somewhat broadly defined as "the ultimate principle of explanation of the universe." He who turns to one principle of explanation will conceive the Absolute in one way, and he who turns to another will, naturally, understand something else by the word. Thus, the idealist may conceive of the Absolute as an all-inclusive Mind, of which finite minds are parts. To Spencer, it is the Unknowable, a something behind the veil of phenomena. Sometimes it means to a writer much the same thing that the word God means to other men; sometimes it has a significance at the farthest remove from this (section 53). Indeed, the word is so vague and ambiguous, and has proved itself the mother of so many confusions, that it would seem a desirable thing to drop it out of philosophy altogether, and to substitute for it some less ambiguous expression.