A double purpose animated Nietzsche in his writing of Beyond Good and Evil which was begun in the summer of 1885 and finished the following winter. It is at once an explanation and an elucidation of Thus Spake Zarathustra, and a preparatory book for The Will to Power. In it Nietzsche attempts to define the relative terms of "good" and "evil", and to draw a line of distintion between immorality and unmorality. He saw the inconsistencies involved in the attempt to harmonize an ancient moral code with the needs of modern life, and recognized the compromises which were constantly being made between moral theory and social practice. His object was to establish a relationship between morality and necessity and to formulate a workable basis for human conduct. Consequently Beyond Good and Evil is one of his most important contributions to a new system of ethics, and touches on many of the deepest principles of his philosophy.