_Consult further_:—F. H. Bradley, _Appearance and Reality_, chap. 22; L. T. Hobhouse, _Theory of Knowledge_, pt. 3, chap. 3; H. Lotze, _Metaphysic_, bk. ii. chaps. 5, 6; H. Münsterberg, _Grundzüge der Psychologie_, i. pp. 65-92; K. Pearson, _Grammar of Science_, chap. 2 (The Facts of Science), 8 (Matter) [mainly written from the “phenomenalist” standpoint, but with unconscious lapses into a more materialistic view]; J. Royce, Nature, Consciousness, and Self-Consciousness” (in _Studies of Good and Evil_); _The World and the Individual_, Second Series, Lect. 4; J. Ward, _Naturalism and Agnosticism_, Lects. 1-5, 14, 19. Of the older philosophical literature, Descartes, _Meditation_ 6; Leibnitz, _Monadology_ and _New System_; Locke, _Essays_, bk. iv. chap. 11; Kant’s “Refutation of Idealism,” in the second edition of the _Critique of Pure Reason_, in addition to the already cited works of Berkeley will probably be found most important. ----- Footnote 119: This definition of the physical order approximates very closely to that adopted by Prof. Münsterberg in his _Grundzüge der Psychologie_, vol. i. pp. 65-77. Prof. Münsterberg defines a _physical_ fact as one which is directly accessible to the perception of a plurality of sentient individuals, as opposed to the psychical fact which can be directly experienced only by one individual. It must be remembered, of course, that my body as directly experienced in “common sensation” and “emotional mood” belongs to the psychical order. It is only my body as perceptible by other men that is a member of the physical order. Footnote 120: Cf. Bradley, _Appearance and Reality_, chap. 22, pp. 260-267 (1st ed.). The attempts which have been made to exempt “primary” qualities from this relativity do not seem to demand serious criticism. The argument in the text applies as directly to extension and shape as to colour or smell. It is not defensible to contend, as Mr. Hobhouse does, that qualities, whether primary or secondary, depend on the percipient organ only for their _perception_, not for their existence. The contention rests upon taking two aspects of experience which are always given together, the _that_ and the _what_ of a sense-content, and arguing that because these two aspects of a single whole can be distinguished, therefore the one can exist in actual separation from the other. It would be quite as logical to infer by the same method and from the same premisses that there can be a perceptive state without any content, as that the contents can exist as we know them, apart from the state. Footnote 121: See particularly the detailed statement of his contention and the elaborate examination of objections in the _Three Dialogues between Hylas and Philonous_, which form a commentary on the briefer exposition of _Principles of Human Knowledge_, §§ 1-134. Footnote 122: