The philosophical legacy of St. Thomas Aquinas (1225–1274) is one of the most enduring in Western thought, profoundly shaping theology, metaphysics, ethics, and political philosophy. His integration of Aristotelian thought with Christian doctrine created a synthesis that continues to influence contemporary discussions in both secular and religious philosophy. To understand the full scope of Aquinas's intellectual project, it is essential to analyze the historical context of the 13th century, the philosophical and theological currents that shaped his work, the primary sources he engaged with, and the foundational concepts he developed.

Aquinas lived in a time of significant intellectual transformation. The 13th century saw the resurgence of Aristotelian philosophy in Europe, largely due to the translation efforts of scholars working in Spain, Sicily, and the Islamic world. The rediscovery of Aristotle, mediated through Islamic philosophers such as Avicenna (Ibn Sina) and Averroes (Ibn Rushd), posed both opportunities and challenges for Christian scholars. Aristotle's philosophy, with its emphasis on empirical observation, causality, and a rational order to the universe, stood in contrast to the predominantly Platonic and Augustinian framework that had dominated medieval Christian thought. Augustine, whose works heavily influenced early medieval theology, had incorporated elements of Neoplatonism, emphasizing the primacy of the divine intellect over material reality and the soul's journey towards God. Aristotle, by contrast, offered a more systematic and naturalistic approach to metaphysics and ethics, one that required careful reconciliation with Christian doctrine.