But how stands the problem of its origin, when, in that which lives, we include the presence of mind? None more firmly contends for the absolute disparity, the entire and unqualified difference between mind and matter, than Mr. Spencer. To him there can be nothing within the whole realm of thought severed by a wider interval than consciousness and thought on the one hand, and matter on the other. ‘Just,’ he says, ‘in the same way that the object is the unknown permanent _nexus_ which is never itself a phenomenon, but is that which holds phenomena together, so is the subject the unknown permanent _nexus_ which is never itself a state of consciousness, but which holds all states of consciousness together.’[22] Mind and matter, then, are here admitted to be infinitely unlike, but absolutely equal realities. This is boldly reaffirmed; he says: ‘No effort of imagination enables us to think of a shock, however minute, except as undergone by an entity. We are compelled, therefore, to postulate a substance of mind that is affected, before we can think of its affections.’[23] [Footnote 22: _Principles of Psychology_, vol. ii. p. 484.] [Footnote 23: _Ibid._ vol. i. p. 627.] This is as clear as a geometric definition. Mind and matter are admitted to be the two opposite termini of thought; they are divided by an interval beyond which thought cannot go. They are symbolized as _x_ and _y_, two equally unknown, but absolutely unlike, quantities. Beyond the common fact of existence, there is not a quality of the one that is not infinitely unlike all the qualities of the other. What this disparity is we all know: enough, that matter is inert, absolutely without perceiving power, and unable in itself to move or to produce motion. But mind is conscious, knows that it exists; and, however mysteriously, originates motion. Matter has mass; mind is absolutely without it. Matter cannot be thought of save as an occupant of space. Mind has no extension. Is it conceivable, then, that we should be required by this philosophy, which thus admits the utter disparity of mind and matter, to make mind a function of matter? that we should be asked to mentally follow a process by which _y_ shall be changed into _x_? This verily is so! I must repeat the formula of this philosophy of evolution. ‘Evolution is an integration of matter, and concomitant dissipation of motion, during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, and during which the retained motion undergoes a parallel transformation.’