A central concern of this work is to honor the Jewish legal scholar and emigrant Rudolf Isay (1886-1956). Additionally, the aim is to restore the significance of Isay's now forgotten work, which deserves recognition due to its visionary power and influence on the development of law. Under these premises, important milestones in Isay's tumultuous and fateful life are first traced, before examining his philosophical, ethical, and economic beliefs. The work then thoroughly addresses Isay's legal creation method, shaped by free law. Based on the insights gained, the most significant treatises of Isay in corporate, patent, antitrust, and competition law are analyzed.