Nietzsche's discussion of these problems is so abstruse and so much complicated by changes in view that it would be impossible to make an understandable summary of it in the space available here. In his first important book, "_Menschliches allzu Menschliches_" he devoted himself, in the main, to pointing out errors made in the past, without laying down any very definite scheme of thought for the future. In the early stages of human progress, he said, men made the mistake of regarding everything that was momentarily pleasant or beneficial as absolutely and eternally true. Herein they manifested the very familiar human weakness for rash and hasty generalization, and the equally familiar tendency to render the ideas of a given time and place perpetual and permanent by erecting them into codes of morality and putting them into the mouths of gods. This, he pointed out, was harmful, for a thing might be beneficial to the men of today and fatal to the men of tomorrow. Therefore, he argued that while a certain idea's effect was a good criterion, humanly speaking, of its present or current truth, it was dangerous to assume that this effect would be always the same, and that, in consequence, the idea itself would remain true forever. Not until the days of Socrates, said Nietzsche, did men begin to notice this difference between imminent truth and eternal truth. The notion that such a distinction existed made its way very slowly, even after great teachers began to teach it, but in the end it was accepted by enough men to give it genuine weight. Since that day philosophy and science, which were once merely different names for the same thing, have signified two separate things. It is the object of philosophy to analyze happiness, and by means of the knowledge thus gained, to devise means for safeguarding and increasing it. In consequence, it is necessary for philosophy to generalize--to assume that the thing which makes men happy today will make them happy tomorrow. Science, on the contrary, concerns itself, not with things of the uncertain future, but with things of the certain present. Its object is to examine the world as it exists today, to uncover as many of its secrets as possible, and to study their effect upon human happiness. In other words, philosophy first constructs a scheme of happiness and then tries to fit the world to it, while science studies the world with no other object in view than the increase of knowledge, and with full confidence that, in the long run, this increase of knowledge will increase efficiency and in consequence happiness.