Every person is conscious, that he is now the same person or self he was, as far back as his remembrance reaches; since, when any one reflects upon a past action of his own he is just as certain of the person who did that action, namely himself, the person who now reflects upon it, as he is certain that the action was at all done. Nay, very often a person's assurance of an action having been done, of which he is absolutely assured, arises wholly from the consciousness that he himself did it. And this he, person, or self, must either be a substance, or the property of some substance. If he, if person, to be a substance; then consciousness that he is the same person, is consciousness that he is the same substance. If the person, or he, be the property of a substance; still consciousness that he is the same property, is as certain a proof that his substance remains the same, as consciousness that he remains the same substance would be; since the same property cannot be transferred from one substance to another.
Joseph Butler, The Analogy of Religion, Dissertation I: Of Personal Identity.
