 This natural law tradition waned in popularity among philosophers during the modern period, with influential early theorists like Hobbes and Hume adopting conventionalist sorts of views. This is of a piece with the turn to more naturalistic views in many different areas of western philosophy, but the tradition never disappeared. Through the works of later natural lawyers in Spain and elsewhere, (Suarez, Molina), the tradition greatly influenced the development of European private law doctrine—the doctrine underlying things like contract and tort law. See the section below on the  relationship between promissory theory and contract law  for more. For an excellent overview of these issues, see chapter 1 of James Gordley’s The Philosophical Origins of Modern Contract Doctrine (1991).