Question

Jacob Katz, of blessed memory, wrote regarding Jewish law (in its broad sense): “In the later stages of its development, especially after the closing of the Talmud, Jewish law took shape as a closed system, whose channels of discussion, the give-and-take through which its matters are clarified, and the mechanism of halakhic ruling attached to it, are sustained by its exclusive sources.”
Is he saying that other fields, such as physics, mathematics, philosophy, etc., cannot help us understand Jewish law? And if so, that is quite astonishing, no? Your writings are the strongest evidence one could bring against him.