All philosophy is in some sense the endeavor to find a unifying principle, to discover the most general conception underlying the whole field of nature and of knowledge.  By one of those bold generalizations which occasionally mark a real advance in Science, Schopenhauer conceived this unifying principle, this underlying unity, to consist in something analogous to that will which self-consciousness reveals to us. Will is, according to him, the fundamental reality of the world, the thing-in-itself; and its objectivation is what is presented in phenomena.  The struggle of the will to realize itself evolves the organism, which in its turn evolves intelligence as the servant of the will.  And in practical life the antagonism between the will and the intellect arises from the fact that the former is the metaphysical substance, the latter something accidental and secondary.  And further, will is desire, that is to say, need of something; hence need and pain are what is positive in the world, and the only possible happiness is a negation, a renunciation of the will to live.

It is instructive to note, as M. Ribot points out, that in finding the origin of all things, not in intelligence, as some of his predecessors in philosophy had done, but in will, or the force of nature, from which all phenomena have developed, Schopenhauer was anticipating something of the scientific spirit of the nineteenth century.  To this it may be added that in combating the method of Fichte and Hegel, who spun a system out of abstract ideas, and in discarding it for one based on observation and experience, Schopenhauer can be said to have brought down philosophy from heaven to earth.

In Schopenhauer’s view the various forms of Religion are no less a product of human ingenuity than Art or Science.  He holds, in effect, that all religions take their rise in the desire to explain the world; and that, in regard to truth and error, they differ, in the main, not by preaching monotheism polytheism or pantheism, but in so far as they recognize pessimism or optimism as the true description of life.  Hence any religion which looked upon the world as being radically evil appealed to him as containing an indestructible element of truth.  I have endeavored to present his view of two of the great religions of the world in the extract which concludes this volume, and to which I have given the title of The Christian System.  The tenor of it is to show that, however little he may have been in sympathy with the supernatural element, he owed much to the moral doctrines of Christianity and of Buddhism, between which he traced great resemblance.  In the following Dialogue he applies himself to a discussion of the practical efficacy of religious forms; and though he was an enemy of clericalism, his choice of a method which allows both the affirmation and the denial of that efficacy to be presented with equal force may perhaps have been directed by the consciousness that he could not side with either view to the exclusion of the other.  In any case his practical philosophy was touched with the spirit of Christianity.  It was more than artistic enthusiasm which led him in profound admiration to the Madonna di San Sisto: