_Tendency of Representative to Absolute Idealism._--It is easy to see how such a doctrine would lead almost inevitably to _absolute idealism_. If we do not in perception take cognizance directly of matter external, but only of certain images or ideas in our own minds, then how do we know that these images _correctly represent_ the external reality, which we have never cognized, and never shall? How do we know, in fact, that there _is_ any such external reality? What evidence have we, in a word, of the existence of any thing beyond and without our own minds? This was the actual result to which Berkley and Hume drove the then prevalent philosophy of Europe, as to a legitimate and inevitable result. _Relation of Dr. Reid to this Controversy._--To Dr. Reid belongs the credit of rescuing philosophy from this dangerous extreme, by showing the utter falsity of the ideal theory. He took the ground that the existence of any such representative images in the mind is wholly without proof, nay more, is inconceivable; that while we can conceive of an image of form or figure, we cannot conceive of an image of sound, or of taste or smell. The hypothesis is wholly without foundation. But even if it were conceivable and established by sufficient evidence, still it would explain nothing as to the manner in which the mind perceives external objects. It relieves no difficulty. If the representative image be itself material, how can the mind take cognizance of it? If not material, how can it represent matter, and how can the mind know that it does represent correctly the external object? _State of the Matter since Reid._--Since the time of Dr. Reid, this theory of representative perception, at least in this non-egoistic form, has been for the most part abandoned, and philosophers have been content to take the ground indicated by consciousness, and the common sense of mankind, that in perception we take direct cognizance of the external object. _Position of Hamilton._--It remained for Sir W. Hamilton to complete the work which Dr. Reid began, by showing that the representative theory, in its finer or egoistic form, as held by Dr. Brown and others, is equally untenable or unsound; that it makes little difference whether we regard the image or idea, which we take to represent the external object, as something distinct from the mind itself, or whether we view it as a mere modification or state of the mind, so long as we make any thing of the sort the direct object of perception instead of the real external thing. Idealism is the result in either case, and philosophical skepticism the goal. In place of any and all such views, Hamilton maintains, with great power and earnestness, the doctrine of natural realism--that in perception we are cognizant immediately and directly of the external object. As no other writer has so fully elaborated this department of science, it may be of service to present in this connection the chief points of his theory.