thesis is the sum and substance of his philosophy. Lacking further light on the point, one can only invoke such experiences as the simple colors, for instance,--or, for that matter, any simple quality--for cases of reality as positive as any heterogeneity, and, obviously, no less qualified. And nothing seems easier than the distinction between redness, for instance, and spatiality. Bergson’s whole dialectic rests on reification of such correlative abstractions as homogeneity and heterogeneity, quality and relation etc. in a “purity” which not only is not concretely experienced, but is not even capable of being conceived, because each concept drags the other ineluctably into its own definition. If either space or homogeneity were indeed absence of quality, they could not be distinguished from time, nor from heterogeneity, nor from anything else; in short, they could not be conceived at all. The present essay aims to report Bergson’s own work with a fair degree of fulness; but it is beyond my plan to follow exposition with criticism point by point in the details, even, in some cases, when these are of important and wide implication. For discussion of Bergson’s contention (based on analysis of the idea of velocity, as outlined above) that mechanics has nothing to do with time, the reader is referred to pages 255-61 of Perry’s _Present Philosophical Tendencies_. Perry shows, in this passage, that such a contention, again, depends on “confusing the symbol with what it means. To one who falls into this confusion, it may appear that an equation cannot refer to time because the structure of the equation itself is not temporal; because the symbols are simultaneously present in the equation. But if _t_ is one of the terms of the equation, and _t_ _means_ time, then the equation means a temporal process. Furthermore, an equation may define a relation, such as =, <, or >, between temporal quantities, in which case the full meaning of the equation is still temporal. For changes, events, or even pure intervals, may stand in non-temporal relations, such as those above, without its in the least vitiating their temporality.”