The attacks that have been made by naturalism upon the independence and freedom of the spiritual are so familiar to every one—even from school days—through books of the type of Büchner’s “Kraft und Stoff,” and Haeckel’s “The Riddle of the Universe,” and other half or wholly materialistic popular dogmatics, that it is unnecessary to enter into any detail. Very little that is new has been added in this connection to the attack made by Plato on himself in the “Phædo” through Simmias and Kebes. It is only apparently that the modern attacks have become more serious through the deepened knowledge of natural science. At all times they have been as serious and as significant as possible, and the religious and every other idealistic conception of the universe has always suffered from them. It is plain that here, if anywhere, “faith goes against appearances,” and that in the last resource we have to postulate free moral resolution, the will to believe, the desire for the ideal, for freedom, and for the eternity of the spirit, and the confidence of the spirit in itself. All this is, or at least ought to be, self-evident and generally admitted. Let us once more take a brief survey of the reasons on the other side and arrange them in order. That nature is everything and spirit very little seems to follow from a very simple circumstance. There are whole worlds of purely natural and corporeal existence without mind, sensation, or consciousness, which, quite untroubled by their absence, simply exist according to the everlasting laws of matter and energy. But nowhere do we find spirit or mind without a material basis. All that is psychical occurs in connection with a physical being, and with relatively few physical beings. Spirit seems wholly bound up with and dependent upon the states, development, and conditions of material being. With the body of living beings there arises what we call “soul”; with the body it grows, gains content, changes, matures, ages, and disappears. According as the body is constituted and composed, as it is influenced by heredity, race, and selection, by nutrition, mode of life, climate, and other circumstances, there are developed in a hundred different ways what we call the natural disposition or character, inclinations, virtues or vices, passions or temperaments. Even the names given to the different temperaments emphasise this dependence of what is innermost in us, the deepest tendencies of our being, on the bodily organisation and the nature of its physiological constitution. The man whose blood flows easily and freely is called sanguine, and the melancholic is the victim of his liver. According as our organs are good or bad, function freely or sluggishly, our mood rises or sinks, we are bold or cowardly, languid or impetuous, and enthusiasm is often enough only a peculiar name for a state which, physiologically expressed, might be called alcoholic poisoning. There is one soul in the sound body, another in the sickly.