We may perhaps hereafter have occasion to note how Descartes, having thus secured one firm foothold and solid resting-place, outwent the farthest stretch of Archimedean ambition by using it, not as a fulcrum from whence to move the world, but as a site for logical foundations whereon he might, if he had persevered, have raised the superstructure of an universe at once mental and material.[32] Intermediately, however, we have to observe how two pre-eminent disciples of the Cartesian school have perverted the fundamental proposition of their great master by treating its converse as its synonyme. Descartes having demonstrated that all thought is existence, Bishop Berkeley and Professor Huxley infer that all existence is thought. So says the Professor in so many words, and to precisely the same effect is the more diffuse language of the Bishop, where, speaking of 'all the choir of heaven and furniture of earth, of all the bodies which compose the mighty frame of the world,' he declares that their _esse_ is _percipi_, that their 'being' consists in their being 'perceived or known,' and that unless they were actually perceived by, or existed in, some created or uncreate mind, they could not possibly exist at all. The reasoning in support of these assertions is in substance as follows:--We know nothing of any material object except by the sensations which it produces in our minds. What we are accustomed to call the _qualities_ of an object are nothing else but the mental sensations of various kinds which the object produces within us. Some of these qualities, such as extension, figure, solidity, motion, and number, are classed as primary; others, as, for instance, smell, taste, colour, sound, as secondary. Now that these latter have no existence apart from mind can readily be shown thus. If I prick my finger with a needle, the pain I suffer in consequence is surely in myself, not in the needle, nor anywhere else but in myself. If an orange be placed on my open hand, my sensation of touching it is in myself, not in the orange. If the orange could feel, what it would feel would be a hand, while what I am feeling is an orange. Nor are my sensations of pain and touch merely confined to myself; they are also confined to a particular part of myself, viz., to the brain, the seat of my consciousness, which it is, and not the finger or hand, that really feels when the one is hurt, or when anything comes in harmless contact with the other. To prove this, let the fine nervous threads, which, running up the whole length of the arm, connect the skin of the finger with the spinal marrow and brain, be cut through close to the spinal cord, and no pain will be felt, whatever injury be done: while if the ends which remain in connection with the cord be pricked, the sensation of pricking in the finger will arise just as distinctly as before. Or let a walking-stick be held firmly by the handle, and its other end be touched, and the