We know of him chiefly from his ten short books on Architecture (_De Architectura, Libri Decem_), in which he touches upon much of the learning of his time. Architecture for Vitruvius is a science arising out of many other sciences. Practice and theory are its parents. The merely practical man loses much by not knowing the background of his activities; the mere theorist fails by mistaking the shadow for the substance. Vitruvius in the theoretical and historical parts of his book draws largely on Greek writers; but in the parts bearing on practice he sets forth, with considerable shrewdness, the outcome of years of thoughtful professional experience. One cannot read his pages without feeling that he is more at home in the concrete than in the abstract and speculative, in describing a catapult than in explaining a scientific theory or a philosophy. He was not a Plato or an Archimedes, but an efficient officer of State, conscious of indebtedness to the great scientists and philosophers. With a just sense of his limitations he undertook to write, not as a literary man, but as an architect. His education had been mainly professional, but, the whole circle of learning being one harmonious system, he had been drawn to many branches of knowledge in so far as they were related to his calling. In the judgment of Vitruvius an architect should be a good writer, able to give a lucid explanation of his plans, a skillful draftsman, versed in geometry and optics, expert at figures, acquainted with history, informed in the principles of physics and of ethics, knowing something of music (tones and acoustics), not ignorant of law, or of hygiene, or of the motions, laws, and relations to each other of the heavenly bodies. For, since architecture "is founded upon and adorned with so many different sciences, I am of opinion that those who have not, from their early youth, gradually climbed up to the summit, cannot without presumption, call themselves masters of it." Vitruvius was far from sharing the view of Archimedes that art which was connected with the satisfaction of daily needs was necessarily ignoble and vulgar. On the contrary, his interest centered in the practical; and he was mainly concerned with scientific theory by reason of its application in the arts. Geometry helped him plan a staircase; a knowledge of tones was necessary in discharging catapults; law dealt with boundary-lines, sewage-disposal, and contracts; hygiene enabled the architect to show a Hippocratic wisdom in the choice of building-sites with due reference to airs and waters. Vitruvius had the Roman practical and regulative genius, not the abstract and speculative genius of Athens.