Problem
George, a farmer, decides to abandon farming and devote himself to the study of philosophy. He worries that so acting might be morally forbidden or contrary to duty. He considers the maxim: "From self-interest, to study philosophy and abandon farming" - but it seems to be rejected by the Formula of Universal Law: if everyone studied philosophy and abandoned farming there would not be sufficient food to support the study of philosophy. But surely it is not contrary to duty to devote you to the study of philosophy! Where has George gone wrong in his use of the Formula of Universal Law?