I have dwelt on this question at much greater length than I should otherwise have done, however interesting it truly is as a question of metaphysics, because I was anxious to obviate a prejudice which is very closely connected with this point, and which, most unfortunately for the progress of the Philosophy of Mind, has given a wrong bias to the speculations of many very enlightened men. No one, I am aware, can be so sincerely sceptical as to doubt, even for a moment, his own identity, as _one continued sentient being_, whatever ingenious sophistry he may urge in support of the paradox which he professes to hold. But still, while the compatibility of diversity with absolute identity, as now explained to you, was but obscurely felt,--a compatibility which, to the best of my remembrance, no writer, with whom I am acquainted, has attempted to illustrate,--the difficulty of reconciling the growth or decay of knowledge, and all the successive contrasts or changes of feeling, which our sensations, thoughts, emotions, exhibit, with the permanent indivisible unity of the same sentient principle, has been sufficient, in many cases, to produce a vague and almost unconscious tendency to materialism, in minds that would not otherwise have been easily led away by a system so illusive; and, where it has not produced this full effect, it has at least produced a tendency, in many cases, to encumber the simple theory of the mental phenomena with false and unnecessary hypotheses, very much akin to those of absolute materialism. Without this absolute materialism, _mind_ must still be left, indeed, as the ultimate subject of sensation, and the difficulty truly remains the same; but it is contrived to complicate, as much as possible, the corporeal part of the process, which precedes this ultimate mental part, by the introduction of phantasms, or other shadowy films, animal spirits, vibratiuncles, or other sensorial motions, that a wider room may thus be left for a play of changes, and the difficulty of accounting for the diversity of sensations be less felt, when it is to be divided among so many substances in almost constant motion; while the attention is, at the same time, led away from the immediate _mental_ change, in which alone the supposed difficulty consists, to the mere _corpuscular_ changes, in which there is no supposed difficulty.