(_d_) Besides these I may mention another error of Timaeus. Having stayed quietly at Athens for about fifty years, during which he devoted himself to the study of written history, he imagined that he was in possession of the most important means of writing it. To my mind this was a great mistake. History and the science of medicine are alike in this respect, that both may be divided broadly into three departments; and therefore those who study either must approach them in three ways. For instance the three departments of medicine are the rhetorical, the dietetic, and the surgical and pharmaceutical. [The second of these though important is discredited by some.][39] The first, which takes its rise from the school of Herophilus and Callimachus of Alexandria, does indeed rightly claim a certain position in medical science; but by its speciousness and liberal promises acquires so much reputation that those who are occupied with other branches of the art are supposed to be completely ignorant. But just bring one of these professors to an actual invalid: you will find that they are as completely wanting in the necessary skill as men who have never read a medical treatise. Nay, it has happened before now that certain persons, who had really nothing serious the matter with them, have been persuaded by their powerful arguments to commit themselves to their treatment, and have thereby endangered their lives: for they are like men trying to steer a ship out of a book. Still such men go from city to city with great _éclât_, and get the common people together to listen to them. But if, when this is done, they induce certain people to submit as a specimen to their practical treatment; they only succeed in reducing them to a state of extreme discomfort, and making them a laughing stock to the audience.[40] So completely does a persuasive address frequently get the advantage over practical experience. The third branch of the medical science, though it involves genuine skill in the treatment of the several cases, is not only rare in itself, but is also frequently cast into the shade, thanks to the folly of popular judgment, by volubility and impudence.