If our knowledge of matter be relative only, our knowledge of mind is equally so. We know it only as susceptible of feelings that have already existed, and its susceptibilities of feelings which have not arisen, but which may, in other circumstances, arise, we know as little, as the blind can be supposed to know of colours, or as we, with all our senses, know of the qualities which matter might exhibit to us, if our own organization were different. Of the _essence_ of mind, then, we know nothing, but in relation to the states or feelings that form, or have formed, our momentary consciousness. Our knowledge is not absolute but relative; though, I must confess, that the term _relative_ is applied, in an unusual manner, when, as in the present instance, the relative and correlative are the same. It is unquestionably the same individual mind, which, in intellectual investigation, is at once the object and the observer. But the noble endowment of memory, with which our Creator has blessed us, solves all the mystery of this singular paradox. In consequence of this one faculty, our mind, simple and indivisible as it truly is, is, as it were multiplied and extended, expanding itself over that long series of sensations and emotions, in which it seems to live again, and to live with many lives. But for memory, there can be no question that the relation of thought to thought could not have been perceived; and that hence there could have been no philosophy whatever, intellectual or moral, physical or metaphysical. To this wonderful endowment, then, which gives us the past to compare with the present, we owe that most wonderful of relations, of which the same being is at once the _object_ and the _subject_, contemplating itself, in the same manner, as it casts its view on objects that are distant from it, comparing thought with thought, emotion with emotion, approving its own moral actions, with the complacency with which it looks on the virtues of those whom it admires and loves, in the most remote nation or age, or passing sentence on itself, as if on a wretch whom it loathed, that was trembling with conscious delinquency, under the inquisition of a severe and all-knowing judge.