“ But Collier did so as far as his light enabled him. He appealed to the popular conviction that the proper object of sense is the sole reality, although he despaired of getting men to give up their belief in its externality, and asserted that nothing but prejudice prevented them from doing so; and there is little doubt that, if it had ever occurred to him, as it did to Berkeley, to explain the genesis of the notion of externality, he would have been more hopeful of commending his theory to the popular mind. ”

“ Both were moved by their dissatisfaction with the theory of representative perception. Both have the feeling that it is inconsistent with the common sense of mankind, which will insist that the very object perceived is the sole reality. They equally affirm that the so-called representative image is the sole reality, and discard as unthinkable the unperceiving material cause of the philosophers. Of objects of sense, they say, their esse is percipi. But Collier never got beyond a bald assertion of the fact, while Berkeley addressed himself to an explanation of it. ”

“ After explaining that he will use the term “external world” in the sense of absolute, self-existent, independent matter, he attempts in the first part to prove that the visible world is not external, by showing—first, that the seeming externality of a visible object is no proof of real externality, and second, that a visible object, as such, is not external. The image of a centaur seems as much external to the mind as any object of sense ”