The concept of substance (both in its broader and narrow significance) transcends all sense-perception. We never sense anything beyond single attributes in varying degrees of relationship to each other; but things or substances are never sensed. We sense color, hardness,tone, &c., but sensation never gives us anything possessing these attributes. We perceive within ourselves a multitude of ever-varying sensations, ideas and feelings, but we never sense a soul or an Ego. That is to say we never discover a constant element which is always present and to which we are justified in ascribing the name Ego. The concept of causality presents a similar case. We perceive distinct phenomena succeeding each other in time; but we do not sense any internal nexus, any necessary connection. Causality is not an object of experience or of perception. (Hume regards the concepts of experience and perception as identical.) It is impossible in this instance to appeal to immediate certainty (intuition), for such procedure is permissible only in cases where the simple relation of equality and inequality can be shown to apply. It is just as impossible, furthermore, to demonstrate causality by the method of inference, for all phenomena and occurrences become matters of experience in the form of independent facts, and it is never possible to infer from the concept of the given fact that the concept of another fact necessarily follows. The motion of a ball, e. g., is something altogether different from the motion of another ball; the one motion can very readily be conceived without the other. The same method of argument applies to the concept of being as to the concepts of substance and causality; no single sensation ever gives us the concept. To take thought about something and to think of it as
