Age of Enlightenment
Hume and other Scottish Enlightenment thinkers developed a 'science of man', which was expressed historically in works by authors including James Burnett, Adam Ferguson, John Millar, and William Robertson, all of whom merged a scientific study of how humans behaved in ancient and primitive cultures with a strong awareness of the determining forces of modernity. Modern sociology largely originated from this movement, and Hume's philosophical concepts that directly influenced James Madison (and thus the U.S. Constitution) and as popularised by Dugald Stewart, would be the basis of classical liberalism.

Q: Whose philosophical concepts directly influenceed James Madison and thus the U.S. Constitution?
Hume