At that time Aristotle published his books of physics and metaphysics. Of this, Alexander who was now in Asia, got information. That ambitious prince, desirous of being in everything the first man in the world, was dissatisfied that the learning of his master should become common. He showed his resentment by the following letter: "You have not done well in publishing your books on speculative science. If what you taught me be taught to men of all ranks, I shall then have nothing but in common with others. But I would have you consider that I had rather be superior to other men in abstract and secret knowledge, than to surpass them in power." To appease this prince Aristotle sent him for answer, that he had published his books, but in such a way that in fact they were not published. By this he apparently meant, that his doctrines were laid down in a manner so embarrassed that it was impossible for any one ever to understand them. Aristotle carefully investigated that question, the great object of moral philosophy, how men might be rendered happy in the present world. In the first place, he refutes the opinion of the voluptuous, who make happiness to consist in corporal pleasures. "Not only," said he, "are these pleasures fleeting, they are also succeeded by disgust; and while they enfeeble the body they debase the mind." He next rejects the opinion of the ambitious, who place happiness in honors, and, with this object in view, pay no regard to the maxims of equity or the restraints of law. "Honor," he said, "exists in him who honors." "The ambitious," he adds, "desire to be honored in consequence of some virtue of which they wish themselves supposed to be possessed; that consequently, happiness consists in virtue, rather than in honors, especially as these are external and do not depend upon ourselves." In the last place, he refutes the system of the avaricious, who constitute riches the supreme good. "Riches," he said, "are not desirable on their own account; they render him who possesses them unhappy, because he is afraid to use them. In order to render them really useful it is necessary to use and to distribute them, and not to place happiness in what is in itself detestable and not worth the having." The opinion of Aristotle is, that happiness consists in the most perfect exercise of the understanding and the practice of the virtues. The most noble exercise of the understanding, he considered to be speculation concerning natural objects; the heavens, the stars, nature, and chiefly the First Being. He observed, however, that without a competency of the good things of fortune suited to a man's situation in life, it was impossible to be perfectly happy, because without this we could neither have time to pursue speculation, nor opportunity to practise the virtues. Thus, for example, one could not please his friends; and to do good to those whom we love is always one of the highest enjoyments of life.