Quantity of Matter originally means the same as amount of resistance to initiation of motion, at first estimated by the varying amount of personal muscular energy required to effect the motion in question, thereafter objectively and scientifically by comparison with some independent standard whereby a more exact estimation can be attained than was possible by a mere reference to the varying inferences of the individual who might exert the force. Space, Mass, Force are all therefore ideas which are furnished to us out of our experience as potent actors, and the recognition of this great truth provides us with the means of clearly apprehending and co-relating our conceptions of the external world, the framework of our Knowledge. The true distinction between a _percept_ and a _concept_ is just that a percept is a concept associated with the dynamic system discovered in and by our exertional activity. In like manner we find here the true solution of the many questions which have been raised as to the distinction between general and abstract, singular and concrete terms. Language expresses action: the roots of language are expressions of the elementary acts which make up experience. They are therefore general. Each applies to every act of the class in question. They are also concrete. That is so because they refer to exertional activities. Abstract terms are terms abstracted from this dynamic reference. Thus _white_ is concrete because colour is a property of the dynamic world. But when this property is considered apart from its dynamic support it is called _whiteness_, and becomes abstract. In the case of purely mental qualities the term is regarded as abstract simply because the quality is in every reference extra dynamic. Thus _candour_, _justice_ are called abstract terms; they are properties of the Mind. But a property of the dynamic system, _e.g._ Gravitation, does not strike us as abstract--the sole distinction being the dynamic reference which the latter term implies. It will even be seen that there is sometimes a shading off of abstract quality. Thus _Justice_ as an attribute of the Mind strikes us as a purely abstract term. But as the word takes up a dynamic reference so does its abstraction diminish. Thus in the expression "Administration of Justice" the abstractive suggestion is less pronounced; till in the person of Justice Shallow it vanishes in the very concrete.