The Summa Theologiae, the work most identified with Aquinas today, was never completed. In December 1273, a few months before his death, he stopped writing altogether after an intense experience during Mass, reportedly telling his companion that everything he had written seemed like straw compared to what had been shown to him.
Historians and theologians have never fully agreed on what to make of this: some read it as a mystical experience that relativized his own scholarship in light of direct vision, others have proposed physical explanations such as a stroke or severe exhaustion, and the sources closest to the event do not resolve the question either way. What followed his death is equally telling about how contested his synthesis of Aristotelian philosophy and Christian theology actually was in its own moment.
In 1277, only three years after he died, the Bishop of Paris condemned a list of philosophical propositions that included several positions closely associated with Thomistic and Aristotelian teaching, a direct institutional rebuke of ideas Aquinas had defended. It took decades for that suspicion to fully lift: he was canonized in 1323, nearly fifty years after his death, and only centuries later given the formal title Doctor of the Church, a reversal from provisional censure to central authority that the Church's own timeline preserves.