cerned with gods, another with men, and the third with the departed. For those who sacrifice according to the laws and take care of the temples are obviously pious towards the gods. Those again who repay loans and restore what they have received upon trust act justly towards men. Lastly, those who take care of tombs are obviously just towards the departed. Thus one species of justice relates to the gods, another to men, while a third species is concerned with the departed. There are three species of knowledge or science, one practical, another productive, and a third theoretical. For architecture and shipbuilding are productive arts, since the work produced by them can be seen. Politics and flute-playing, harp-playing and similar arts are practical. For nothing visible is produced by them; yet they do or perform something. In the one case the artist plays the flute or the harp, in the other the politician takes part in politics. Geometry and harmonics and astronomy are theoretical sciences. For they neither perform nor produce anything. But the geometer considers how lines are related to each other, the student of harmony investigates sounds, the astronomer stars and the universe. Thus some sciences are theoretical, others are practical, and others are productive. There are five species of medicine: the first is pharmacy, the second is surgery, the third deals with diet and regimen, the fourth with diagnosis, the fifth with remedies. Pharmacy cures sickness by drugs, surgery heals by the use of knife and cautery, the species concerned with diet prescribes a regimen for the removal of disease, that concerned with diagnosis proceeds by determining the nature