Most would understand the phrase that the mind of More was like a diamond that a tyrant threw away into a ditch, because he could not break it. It is but a metaphor; but it does sometimes happen that the metaphor is many-sided, like the diamond.
What moved the tyrant to a sort of terror of that mind was its clarity; it was the very reverse of a cloudy crystal filled only with opalescent dreams or visions of the past. The King and his great Chancellor had been companions as well as contemporaries; in many ways, both were Renaissance men; but in some ways, the man who was the more Catholic was the less medieval.
That is, there was perhaps more in the Tudor of that mere musty fag-end of decayed medievalism, which the real Renaissance reformers felt to be the corruption of the time. In More’s mind there was nothing but clarity; in Henry’s mind, though he was no fool and certainly no Protestant, there was something of confused conservatism. Like many a better man who is an Anglo-Catholic, he had a touch of the antiquary. Thomas More was a better rationalist, which was why there was nothing in his religion that was merely local, or in that sense merely loyal.
More’s mind was like a diamond also in a power like that of cutting glass; of cutting through things that seemed equally transparent, but were at once less solid and less many-sided. For the true consistent heresies generally look very clear indeed; like Calvinism then or Communism now. They sometimes even look very true; they sometimes even are very true, in the limited sense of a truth that is less than the Truth. They are at once more thin and more brittle than the diamond. For a heresy is not often a mere lie; as Thomas More himself said, “Never was there a heretic that spoke all false.” A heresy is a truth that hides all the other truths. A mind like More’s was full of light like a house made of windows; but the windows looked out on all sides and in all directions. We might say that, as the jewel has many facets, so the man had many faces; only none of them were masks. –from The Well and the Shallows (1935)