  The main origins of the subject lie in the early 20th century in the work of the French analysts Borel, Baire, and Lebesgue. The subject grew into an independent discipline through the work of the Russian mathematician Luzin (who had learned of the subject as a student while in Paris) and was developed by his students, most notably Suslin. The end of this early period of descriptive set theory was marked by a major theorem proved by the Japanese mathematician Kondô in 1937. After nearly 40 years of development, progress came to an abrupt halt. The explanation for this was eventually provided by the independence results of Gödel and Cohen (in 1938 and 1963). For, using this machinery, it was shown that the open questions that the early descriptive set theorists were trying to answer could not be resolved on the basis of the standard axioms of mathematics, ZFC. It is a testament to the ingenuity of the early descriptive set theorists that they had developed their subject right up to the edge of undecidability. 