The mention of material substance naturally suggests the doctrine of 'materialism,' but philosophical materialism is not necessarily knit up with belief in 'matter,' as a metaphysical principle. One may deny matter in that sense, as strongly as Berkeley did, one may be a phenomenalist like Huxley, and yet one may still be a materialist in the wider sense, of explaining higher phenomena by lower ones, and leaving the destinies of the world at the mercy of its blinder parts and forces. It is in this wider sense of the word that materialism is opposed to spiritualism or theism. The laws of physical nature are what run things, materialism says. The highest productions of human genius might be ciphered by one who had complete acquaintance with the facts, out of their physiological conditions, regardless whether nature be there only for our minds, as idealists contend, or not. Our minds in any case would have to record the kind of nature it is, and write it down as operating through blind laws of physics. This is the complexion of present day materialism, which may better be called naturalism. Over against it stands 'theism,' or what in a wide sense may be termed 'spiritualism.' Spiritualism says that mind not only witnesses and records things, but also runs and operates them: the world being thus guided, not by its lower, but by its higher element. Treated as it often is, this question becomes little more than a conflict between aesthetic preferences. Matter is gross, coarse, crass, muddy; spirit is pure, elevated, noble; and since it is more consonant with the dignity of the universe to give the primacy in it to what appears superior, spirit must be affirmed as the ruling principle. To treat abstract principles as finalities, before which our intellects may come to rest in a state of admiring contemplation, is the great rationalist failing. Spiritualism, as often held, may be simply a state of admiration for one kind, and of dislike for another kind, of abstraction. I remember a worthy spiritualist professor who always referred to materialism as the 'mud-philosophy,' and deemed it thereby refuted. To such spiritualism as this there is an easy answer, and Mr. Spencer makes it effectively. In some well-written pages at the end of the first volume of his Psychology he shows us that a 'matter' so infinitely subtile, and performing motions as inconceivably quick and fine as those which modern science postulates in her explanations, has no trace of grossness left. He shows that the conception of spirit, as we mortals hitherto have framed it, is itself too gross to cover the exquisite tenuity of nature's facts. Both terms, he says, are but symbols, pointing to that one unknowable reality in which their oppositions cease.