regarded. We have already remarked that it was but the stepping-stone or prelude to those maturer and more extended doctrines of idealism in which his genius afterwards expatiated, and which have made his name famous throughout every corner of the philosophic world; and which we have endeavoured to do justice to in the preceding pages, giving a more enlarged and unobjectionable construction to their principle, and clearing, we think, at least some of the difficulties which beset his statement of it. His theory of vision may be called an essay on the idealism of the eye, and of the eye alone. It is idealism restricted to the consideration of this sense, and is the first attempt that ever was made to embody a systematic and purely speculative critique of the facts of seeing. We use the words purely speculative in contradistinction from geometrical and physiological critiques of the same sense; of which there were abundance in all languages, but which, proceeding on mathematical or anatomical data, which are entirely tactual, had, in Berkeley's opinion, nothing whatever to do with the science of optics, properly so called. Optics, as hitherto treated, that is to say, as established on mathematical principles, appeared to him to be a false science of vision; for this reason, that the blind were found to be just as capable of understanding and appreciating it, as those were who could see. Hence he concluded, and most justly, that the true facts of sight had been left out of the estimate, because these were, and necessarily
