66. Mental Phenomena.

Material objects are all either not living, that is to say, mineral bodies, or they are living bodies. Everything which occupies space, offers resistance, has weight and transfers motion, belongs to one or other of these two great provinces of nature. The sciences of Astronomy, Mineralogy, Physics, and Chemistry deal with the former, while Biology, with its two divisions of Zoology and Botany, treats of the latter. But natural knowledge is not exhausted by this catalogue of its topics. In the very first paragraph of this Primer, in fact, we had occasion to draw a distinction between Things, or material objects, and Sensations; and a moment’s reflection is sufficient to convince you that sensations are not material objects. A smell takes up no space and has no weight; and to speak of a pound or of a cubic foot of sound, or of brightness, is, on the face of the matter, an absurdity. Pleasure is said metaphorically to be fugitive, but you cannot imagine a pleasure as a thing in motion.

What we call our Emotions are in like manner devoid of all the characters of material bodies. Love and hatred, for example, cannot for a moment be conceived to have shape, or weight, or momentum. And when, in reasoning, we think, our Thoughts have the same lack of the qualities of material things.

Sensations, emotions, and thoughts, thus constitute a peculiar group of natural phenomena, which are termed mental.

67. The order of Mental Phenomena: Psychology.

A definite order obtains among mental phenomena, just as among material phenomena; and there is no more chance, nor any accident, nor uncaused event, in the one series than there is in the other. Moreover, there is a connection of cause and effect between certain material phenomena and certain mental phenomena. Thus, for example, certain sensations are always produced by the influence of particular material bodies on our organs of sense. The prick of a pin gives pain, feathers feel soft, chalk looks white, and so on. The study of mental phenomena, of the order in which they succeed one another, and of the relations of cause and effect which obtain between them and material phenomena, is the province of the science of Psychology.

All the phenomena of nature are either material or immaterial, physical or mental; and there is no science, except such as consists in the knowledge of one or other of these groups of natural objects, and of the relations which obtain between them.