George Stuart Fullerton (1859–1925) was a prominent American philosopher and psychologist, whose scholarly contributions extend across a breadth of discipline from the mind's intricacies to ethical theory's foundational concepts. Fullerton's legacy in philosophical literature is cemented by his influential texts, particularly 'A Handbook of Ethical Theory' (1922), which offers a systematic and thorough exposition of ethical principles, underscoring the complexity of moral philosophy. Educated at the University of Pennsylvania and in Germany at the Universities of Berlin and Leipzig, Fullerton was deeply influenced by the German philosophical tradition, particularly the work of Kant and the idealists. As a professor at the University of Pennsylvania and later at Columbia University, he specialized in epistemology and ethics, propelling American philosophical thought forward during the late 19th and early 20th centuries. Fullerton's writing style encapsulated clarity and precision, revealing his earnest endeavor to make philosophical concepts accessible to a broader audience. Through his teachings and writings, Fullerton played a pivotal role in the professionalization and development of philosophy and psychology as distinct academic disciplines in the United States. His other notable works include 'An Introduction to Philosophy' (1915), where he disseminates complex philosophical ideas with remarkable lucidity, facilitating a gateway for students into the world of philosophical thought.