familiar to the ordinary English mind. But the inconsistencies we have already found inherent in such a conception of Substance as is here presupposed, so inevitably make themselves felt upon any serious examination, that the doctrine regularly appears in the history of thought as a mere temporary halting-place in the advance to the more radical notion of matter as the entirely unknown non-phenomenal substratum of the sensible properties of bodies. § 2. This latter notion is again manifestly open to all the objections previously brought against the more general concept of substance as an unknown substratum or support of properties. It is from these objections that Berkeley’s famous criticism of the concept of matter, the most original attempt at a constructive theory of the real nature of the physical order in the history of English Philosophy, starts. Berkeley first takes the identification of material substance with the primary qualities of body, which Locke had made current in English speculation, and shows, by insisting upon the relativity of perceived quality to percipient organ, that it is untenable. Having thus driven his opponent to surrender this identification, and to define matter as the unknown substratum of the physical order, he proceeds to argue that this notion of an unknown substratum is both useless and unintelligible. It is useless, because our knowledge of the actual properties and processes of the physical order can neither be extended nor made clearer by the addition of an unknowable; it is unintelligible, because we can give no account to ourselves of the nature of the “support” supposed to be bestowed by the substratum or the properties.