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Who was St. Thomas Aquinas, and why did his ideas become influential in Roman Catholic theology?

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St. Thomas Aquinas Enthroned Between the Doctors of the Old and New Testaments, with Personifications of the Virtues, Sciences, and Liberal Arts, fresco by Andrea da Firenze, c. 1365; in the Spanish Chapel of the Church of Santa Maria Novella, Florence. — Thomism *St. Thomas Aquinas Enthroned Between the Doctors of the Old and New Testaments, with Personifications of the Virtues, Sciences, and Liberal Arts*, fresco by Andrea da Firenze, c. 1365; in the Spanish Chapel of the Church of Santa Maria Novella, Florence.

St. Thomas Aquinas (1224/25–1274) was an Italian Dominican theologian and the foremost medieval Scholastic. He is recognized by the Roman Catholic Church as its preeminent Western philosopher and theologian, known for his masterpieces, the Summa theologiae and the Summa contra gentiles.12

Aquinas’s ideas became influential because he successfully harmonized Aristotelian philosophy with Christian doctrine. He argued that reason and faith originate from the same divine source and cannot contradict one another. By using Aristotelian logic to explain theological concepts, he provided a rigorous framework for Christian thought.3

His influence was solidified over centuries:
* Institutional Adoption: In 1879, Pope Leo XIII issued the encyclical Aeterni Patris, which called for a restoration of Thomistic philosophy to defend the faith against modern secular ideologies.4
* Official Status: In 1917, the Code of Canon Law mandated that Catholic teachers follow the principles and methods of Aquinas, establishing Thomism as the official philosophy of the Church.4