He sought to steer a middle course between traditional natural law theory and legal positivism. He rejected traditional religious forms of natural law theory, which view human law as rooted in a rationally knowable and universally binding 'divine law' that derives from God. He criticized legal positivism and defended a secular and procedural form of natural law theory In his widely discussed book, The Morality of Law, he argues that all systems of law contain an "internal morality" that imposes on individuals- a presumptive obligation of obedience. Who was this legal philosopher: