Have animals no memory? It will be replied, the contrary seems demonstrably evident. After a considerable absence do they not recognize the persons with whom they had lived, the places where they resided, and the roads which they had frequented? Do they not recollect the punishments, the caresses, the lessons they had received? Though deprived of imagination and understanding, every thing seems still to evince they have a memory active, extensive, and perhaps more faithful than our own. However persuasive these appearances may be deemed, and however strong may be the prejudices created by them, I presume I can demonstrate, that they deceive us, and that brute animals have no knowledge of past events, no idea of time, and of consequence no memory. In man memory flows from the power of reflection, for the remembrance of things past supposes not only the duration of the impressions on our internal material sense, or renovation of former sensations, but also the comparison which the mind has made of those sensations, or the ideas it has formed. If memory consisted merely in the renovation of past sensations, those sensations would be represented to our internal sense without leaving any determined impressions; they would present themselves without order or connection, as they do in a state of intoxication, or in dreams, when they are so incongruous, and so incoherent, that we immediately lose all recollection of them. Of such things only as have a relation to others, which preceded or followed them, do we retain a remembrance; and every solitary sensation, however powerful, passes away without leaving the smallest trace on the mind. Now it is the mind which establishes these relations of objects, by the comparison it makes between them, and connects our sensations by a continued thread of ideas. As memory consists, then, in a succession of ideas, so it necessarily supposes the power by which ideas are produced. But, if possible, to leave no doubt on this important point, let us enquire into the nature of that remembrance left by our sensations when they are accompanied with ideas. Pain and pleasure are pure sensations, and the strongest of any, yet we but feebly recollect them, and with confusion. All we remember is, that we were pleased or hurt; but this remembrance is not distinct; we cannot represent to ourselves either the kind, the degree, or the duration of those sensations by which we had been so violently agitated; and the less are we capable of representing those we had but seldom felt. A pain, for example, which we have experienced but once, which only lasted a few minutes, and differed from all former pains, would be soon forgotten; we might recollect we felt great pain, yet, though we distinctly recollected the circumstances which accompanied it, and the period at which it happened, we should have but an imperfect remembrance of the pain itself.