Cicero was the first to systematize the philosophy which contributed so greatly to his intellectual culture, But even he added nothing; he was only a commentator and expositor. Nor did he seek to found a system or a school, but merely to influence and instruct men of his own rank. Those subjects which had the greatest attraction for the Grecian schools Cicero regarded as beyond the power of human cognition, and therefore looked upon the practical as the proper domain of human inquiry. Yet he held logic in great esteem, as furnishing rules for methodical investigation. He adopted the doctrine of Socrates as to the pursuit of moral good, and regarded the duties which grow out of the relations of human society as preferable to those of pursuing scientific researches. He had a great contempt for knowledge which could lead neither to the clear apprehension of certitude nor to practical applications. He thought it impossible to arrive at a knowledge of God, or the nature of the soul, or the origin of the world; and thus he was led to look upon the sensible and the present as of more importance than inconclusive inductions, or deductions from a truth not satisfactorily established. Cicero was an eclectic, seizing on what was true and clear in the ancient systems, and disregarding what was simply a matter of speculation. This is especially seen in his treatise "De Finibus Bonorum et Malorum," in which the opinions of all the Grecian schools concerning the supreme good are expounded and compared. Nor does he hesitate to declare that the highest happiness consists in the knowledge of Nature and science, which is the true source of pleasure both to gods and men. Yet these are but hopes, in which it does not become us to indulge. It is the actual, the real, the practical, which pre-eminently claims attention,--in other words, the knowledge which will furnish man with a guide and rule of life. Even in the consideration of moral questions Cicero is pursued by the conflict of opinions, although in this department he is most at home. The points he is most anxious to establish are the doctrines of God and the soul. These are most fully treated in his essay "De Natura Deorum," in which he submits the doctrines of the Epicureans and the Stoics to the objections of the Academy. He admits that man is unable to form true conceptions of God, but acknowledges the necessity of assuming one supreme God as the creator and ruler of all things, moving all things, remote from all mortal mixture, and endued with eternal motion in himself. He seems to believe in a divine providence ordering good to man, in the soul's immortality, in free-will, in the dignity of human nature, in the dominion of reason, in the restraint of the passions as necessary to virtue, in a life of public utility, in an immutable morality, in the imitation of the divine.