But there has ever been a tendency to emphasise one or other of these aspects. The question has constantly arisen, Which is the more important for life--what we receive or what we create? Accordingly two contrasted conceptions of life have appeared--a naturalistic and an idealistic. Under the first we understand those theories which place man in the realm of sense and explain life by material conditions; under the second we group such systems as give to life an independent creative power. I NATURALISTIC TENDENCY 1. Naturalism has usually taken three forms, an idyllic or poetic, a philosophic, and a scientific, of which Rousseau, Feuerbach, and Haeckel may be chosen as representatives. (1) According to Rousseau, man is really a part of nature, {101} and only as he conforms to her laws and finds his satisfaction in what she gives can he be truly happy. Nature is the mother of us all, and only as we allow her spirit to pervade and nourish our being do we really live. The watchword, 'back to nature' may be said to have given the first impulse to the later call of the 'simple life,' which has arisen as a protest against the luxury, ostentation, and artificiality of modern times. (2) The philosophical form of naturalism, as expounded by Feuerbach, inveighs against an idealistic interpretation of life. The author of _The Essence of Christianity_ started as a disciple of Hegel, but soon reversed the Hegelian principle, and pronounced the spiritual world to be a fiction of the mind. Man belongs essentially to the earth, and is governed by his senses. Self-interest is his only motive, and egoism his sole law of life. It was only what might be expected, that the ultimate consequences of this philosophy of the senses should be drawn by a disciple of Feuerbach, Max Stirner,[1] in whose work, _The Individual and His Property_, the virtues of egoism are extolled, and contempt is poured upon all disinterestedness and altruism.