In his essays About Beliefs (1931) Chesterton writes the following on the similarity between Medicine and Magic, and how the Greeks understood the scientific knowledge:
..that Magic (in the ancient sense) and Medicine (in the modern sense) are really in one way very like each other, because they are both very unlike the pure and abstract idea of Science as conceived by the Ancient Greeks. Science only means knowledge; and for those ancients it did only mean knowledge. They wanted nothing but the pleasure of knowing; they were particularly proud of knowing a great deal of utterly useless knowledge. Thus the favourite science of the Greeks was Astronomy, because it was as abstract as Algebra. And when the Philistine among them said: “What are the Pleiades to me?” the Philosopher really answered the Philistine by saying: “They are all the more to me because they are nothing to me.” We may say that the great Greek ideal was to have no use for useful things. The Slave was he who learned useful things; the Freeman was he who learned useless things. This still remains the ideal of many noble men of science, in the sense that they do desire truth as the great Greeks desired it; and their attitude is an eternal protest against the vulgarity of utilitarianism. But there was and is another side of science, also to be respected, which was from the first represented by things like Medicine. And if there were some association of Medicine with Magic, it was because Magic was always extremely practical.