In the “Scientific Proceedings of the Royal Dublin Society” (Vol. VI, Part IX, p. 475, 1890), Dr. Johnstone Stoney, F. R. S., published an interesting and carefully-reasoned paper “On the Relation between Natural Science and Ontology.” The same author had previously (1885), in a Friday evening discourse at the Royal Institution of London, discussed the problem, “How Thought Presents Itself Among the Phenomena of Nature.” Dr. Stoney’s communications have not (I venture to think) received the consideration to which they are entitled alike on the score of their logical consistency, if his premisses and assumptions be granted, and by reason of the author’s scientific eminence as a physicist. I therefore propose, first, to endeavor to set forth his monistic _Doctrine of Auta_; and secondly, to offer some criticisms thereon. Unfortunately Dr. Stoney’s pages bristle with new technical terms, which, though no doubt they have been serviceable to him in the attainment of precision of thought, make his paper hard reading. Some of these I shall introduce; others which seem less essential to the argument I shall omit. It would be scarcely fair on the reader’s teeth or on the author’s store to transfer all these hard nuts from Dublin to Chicago. No philosophical discussion of a problem involving perception can be regarded as complete without the introduction of an orange. Dr. Stoney, indeed, substitutes a fire; but this, though it shows philosophical independence, cannot for a moment be sanctioned by any good Berkeleyan. An orange then, as such, is a phenomenal object formed, in a way we need not now consider, by the synthesis of perceptions. These perceptions, themselves synthetic, Dr. Stoney calls “tekmeria,” since they are signs within my mind that events are happening in a part of the universe that is distinct from my mind. The phenomenal object is supposed by men untrained in inquiries relating to the mind to have a non-egoistic existence—that is, an existence independent of the percipient mind. But this supposition is found on careful scrutiny to be an error. It is a product of mental synthesis, and is therefore termed by Dr. Stoney a “syntheton.” It is also termed a “protheton” in contradistinction to an “antitheton,” which we shall come to shortly.