Again, let me note the relation of intensity, and consequently feeling of intensity, to quantity of consciousness—a subject suggested by Mr. Sully (_Mind_, xiii. 252). The fundamental properties of consciousness—quality, quantity, intensity—and also their inter-relations, would be a fruitful theme for extended discussion. I think that the clearing-up of many problems would result from thorough investigation and careful definition in these points; but at present I can only offer a remark or two upon the subject. It is plain that intensity varies with different qualities, that certain kinds of mental action are more generally characterised by high degrees of intensity than others. Presentations tend to higher intensities than representations, and pains than pleasures. It is noticeable that our psychological nomenclature, both popular and scientific, is mostly concerned with qualities, which shows that quantities and intensities have not received the attention they deserve, and have not been carefully discriminated. A representation of the same house comes up in the minds of two persons, one of whom has lived in it, the other merely seen it several times. Each psychosis is as representative as the other: they have the same quality, but in quantity and intensity they vary greatly. In a single multiplex act of consciousness, the former embraces a wide reach of detail and association and a high degree of intensity which is lacking in the meagre and faint image of the latter. Physiologically, quantity is as the mass of co-ordinate coincident activities of brain in highest centres, and intensity is as the arterial and nervous tension in the highest centres. Intensities may be equal, and quantities very unequal; as compare one greatly interested in a game of cards with a person watching a near relative at a critical moment of illness. Intensity of pleasurable hope alternating with painful fear may be equal in both cases, but in quantity the latter would tend to exceed. Very quiet natures are often characterised by largeness of quantity of consciousness. Other things being equal, intensity tends to reduce quantity and obscure quality of consciousness. Quantity, like intensity, may cause a reflex act of consciousness when it becomes so great as to push into consciousness as recognition and feeling of quantity; and as a feeling of largeness, elevation and mental power it is clearly distinguishable from excitement as feeling of intensity. Intensity is dependent on the force or strength by which a mental state tends to persist against other states which may be crowding in, and it is also closely connected with rapidity of mental movement; but it is primarily tension, consciousness at its highest stretch, specially as touching upon interest, an element more or less involved in all consciousness.