Furthermore, the scientific ignorance of the ancients is exaggerated. Ancient science is not so well-known as ancient art and literature; and it certainly did not make very striking progress during the last brilliant period of ancient history—the Roman Empire. Therefore to many, whose knowledge regarding it is comparatively superficial, the ancient world may seem empty of scientific wisdom. But such is not the case. If the Romans never applied much thought to the scientific study of nature, the Greeks for their part had laid the foundations of many sciences, and had laid them boldly and truly. Even the Copernican system had been anticipated by Greek astronomers, like Aristarchus of Samos and Seleucus of Seleucia, who had maintained that the earth revolved round the sun, and that the firmament was much more vast than was generally supposed. We need not, therefore, believe that the ancients were not able to construct more complicated machines than those they used, because they lacked scientific knowledge. It would be nearer the truth to say that they did not make much effort to raise sciences out of the necessarily narrow domain of purely theoretical problems, because, independent as they were of machinery, they had no need of the practical aids which science, if developed in certain directions, can lend to the construction of machines. In fact, we men of the present day encourage the sciences to search and investigate in every direction and to try every path, not from a disinterested love of the True nor from an intellectual curiosity to spy out the mysteries of nature; but because we hope that we shall discover, in the course of our all-embracing search, laws or bodies or forces which will help us to subdue and exploit nature.