Humility

His contemporaries most frequently commented on Thomas's humility, a virtue little prized in our times, since we seem unable to distinguish between the humble person's self-evaluation from what we call low self-esteem. In consequence, self-assertion takes on the appearance of a virtue, merely by way of contrast with that mistaken conception of humility. Humility, in sense of that his contemporaries observed its presence in Thomas, had more to do with that peculiarly difficult form of vulnerability, which consists in being entirely open to the discovery of the truth, especially to the truth about oneself. One might say, likewise, that what humility is to the moral life, lucidity is to the intellectual ˗ an openness to contestation, the refusal to hide behind the opacity of the obscure, a vulnerability to refutation to which one is open simply as a result of being clear enough to be seen, if wrong, to be wrong.

We might say, then, that Thomas was fearlessly clear, unafraid to be shown to be wrong, and correspondingly angered by those among his colleagues, especially in the University of Paris, who in his view refused to play the game on a field levelled by lucidity and openness equal in degree of honesty to the requirements of the intellectual life. And yet, even in Thomas’s anger there is nothing personal. His is the anger of a true teacher observing students to have been betrayed by colleagues. It has no more to do with self-assertion than his humility has to do with lack of self-worth. 

From Thomas Aquinas: a portrait, by Denys Turner, pages 39-40