Science and the humanities share the same kit of working tools, called the world's literature. While the author of this article deals mainly with the scientific and mathematical literature, the reader probably gravitates towards some other branches, but such distinctions were hardly made in the Middle Ages. The American philosopher, Wallace Stevens, in his book The Necessary Angel remarks that at the time of Aristotle, the Greek language had no word to signify literature. The reason is surely that literature had long since been too universal an element in Greece to require a name. We have no name for the smell of air. This all-pervading power of literature is apparent already two generations before Aristotle, when Socrates made his defence against leading the youth of Athens towards atheism. Plato's Apology tells us how Socrates taunted his accuser: “Have you such a low opinion of the judges, that you fancy them so illiterate as not to know these doctrines are found in the books of Anaxagoras which are full of them? And so, my word, the youth are said to be taught them by Socrates, when they can be bought in the book-market for one drachma at most…” (a coin today worth 1.4 pence!).