_Thirdly_, 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 who now reflects upon it, as he is certain that the action was done at all. 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. This he, person, or self, must either be a substance, or the property of some substance. If he, a person, 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. But though we are thus certain, that we are the same agents, living beings, or substances, now, which we were as far back as our remembrance reaches; yet it is asked, whether we may not possibly be deceived in it? And this question may be asked at the end of any demonstration whatever: because it is a question concerning the truth of perception by memory. He who can doubt, whether perception by memory can in this case be depended upon, may doubt also, whether perception by deduction and reasoning, which also include memory, or indeed whether intuitive perception can. Here then we can go no further. For it is ridiculous to attempt to prove the truth of those perceptions, whose truth we can no otherwise prove, than by other perceptions of exactly the same kind with them, and which there is just the same ground to suspect; or to attempt to prove the truth of our faculties, which can no otherwise be proved, than by the use or means of those very suspected faculties themselves.[305] DISSERTATION II. The Nature of Virtue.