'Conceptualism' is the metaphysical doctrine now prevalent with respect to general ideas. They are regarded not as objects nor as essences, but as forms of consciousness depending more or less on our own mental activity. This is true enough so far as it goes, but without a substantial plasm to hold the 'concept' its formation and endurance are quite inexplicable. XIII--MATTER Matter is the name given to the most general idea we can form of objects. It is supposed to cover all of them. In other words, the content or 'essence' of the idea is the attribute or attributes common to all objects without exception. It is the universal objective minimum--the least objective experience consistent with the experience being objective. Some have attempted to define this general idea more precisely by identifying it with some _abstract_ property such as extension, resistance, etc. An object may be material without offering any resistance to human energy, as a beam of light. A material object may also be without extension, as a sound or smell. The only quality left to matter is bare objectivity, namely, that it is a form of consciousness excited in a mind by some other mind, not occurring spontaneously. This seems to me the only true connotation of matter. Matter is not the antithesis of mind; it is a mere affection of mind. The two are not in any proper sense co-ordinate or equipollent. They are to each other somewhat in the relation of a mirror to an image reflected from it. Mind is to each of us a concrete primary experience--the feeling of personal power and identity. Matter is a general idea arising from the comparison of objects in consciousness. No two things could well be more diverse. Since general ideas are products of our own mental energy, and matter the most general of all, it is the farthest removed from the concrete objective condition, and so it is literally true that we never objectively perceive matter though we constantly perceive material objects. It is as impossible to see, touch, or taste matter as it is to ride the general idea _Equus_ or dine off the general idea _nourishment_. In denying the objectivity of matter we do not deny the objective reality of things: we merely decline to confound a general idea with the objects that have contributed to form it. We decline to be _mystics_, in the sense defined by J. S. Mill[10]. The belief in the external existence of matter is a form of mysticism; the Hindus call it _maya_, meaning illusion. Some metaphysicians argue that since phenomena appear only in conjunction, we are compelled by the constitution of our nature to think of them conjoined in and by something, and this imaginary foundation and cement is another meaning of the word 'matter.'