For obviating this tendency to _materialism_, or to what may be considered almost as a species of _semi-materialism_ in the physiology of the mind, it is of no small consequence to have accurate views of the nature of our mental identity. Above all, it is of importance, that we should be sufficiently impressed with the conviction, that absolute identity, far from excluding every sort of diversity, is perfectly compatible, as we have seen, with diversities that are almost infinite. When we have once obtained a clear view of this compatibility, as independent of any additions or subtractions of substance, we shall no longer be led to convert our simple mental operations into long continued processes, of which the last links only are mental, and the preceding imaginary links corporeal; as if the introduction of all this play of hypotheses were necessary for saving that identity of mind, which we are perhaps unwilling to abandon altogether; for it will then appear to us not more wonderful, that the _mind_, without the slightest loss of identity, should at one moment begin to exist in the state which constitutes the sensation of the fragrance of a rose, and at another moment should begin to exist in the state which constitutes the sensation of the sound of a flute, or in the opposite states of love and hate, rapture and agony--than that the same _body_, without the slightest change of its identity, should exist, at one moment, in the state which constitutes the tendency to approach another body, and at another moment in the opposite state which constitutes the tendency to fly from it, or that, with the same absolute identity, it should exist, at different moments in the different states, which constitute the tendencies to begin motion in directions that are at right angles to each other, so as to begin to move in the one case north, in the other east, and to continue this motion, at one time with one velocity, at other times with other velocities, and consequently, with other tendencies to motion that are infinite, or almost infinite.