Introspective psychology bears witness to the same truth; for consciousness reinforced by memory attests _the substantial permanence of our personal identity_. We both think and regulate our practical conduct in accordance with this sense of unchanging personal identity. All recognition of the past means simply this, that we perceive the substantial identity of our present, with our past, selves throughout all the experiences and vicissitudes of life. There is an inmost core of our being which is unchanging and which remains always identical with itself, in spite of the flow of thought and the metabolic changes of the life-cycle. It is this that gives us the sense of being always identically the same person, from infancy to maturity, and from maturity to old age. It is this that constitutes the thread of continuity which links our yesterdays with today, and makes us morally responsible for all the deliberate deeds of a lifetime. Courts of law do not acquit a criminal because he is in a different frame of mind from that which induced him to commit murder, nor do they excuse him on the score that metabolism has made him a different mass of flesh from that which perpetrated the crime. Such philosophies as phenomenalism and materialism are purely academic. Even their advocates dare not reduce them to consistent practice in everyday life. Nor can the cases of _alternating personalities_ be adduced as counterevidence. In the first place, these cases are psychopathic and not normal. In the second, they are due, not to a modification of _personality itself_, but to a modification in the _perception of personality_. Since this perception is, as we shall see, extrinsically dependent on cerebral imagery, any neuropathic affection is liable to modify the perception of personality by seriously disturbing the imagery, on which it depends. But (_pace_ Wundt and James) the perception of personality is one thing, and personality itself quite another. Perception does not produce its objects, but presupposes them, and self-perception is no exception to this rule. Introspection, therefore, does not create our personality, but reveals and represents it. If then to the intuition of consciousness our personality appears as an unchanging principle that remains always substantially identical with itself, it follows that this perception must be terminated by something more durable than a flux of transient molecules or a stream of fleeting thought. Unless this perceptive act has for its object some unitary and uniformly persistent reality distinct from our composite, corruptible bodies, and not identified with our transitory thoughts, this sense of permanent personal identity would be utterly impossible. Materialism, which recognizes nothing more in man than a decaying organism, a mere vortex of fluent molecules, is at a loss to account for our consciousness of being always the same person. Phenomenalism,