TIME magazine’s pronouncement of Pope Francis as “Person of the Year,” coming as it does after yesterday’s memorial service for Nelson Mandela, has sparked some thoughts on the making of these two great persons.  What unites them? A surprising number of things, maybe, but one quality in particular stands out.

Humility, in a willingness to be treated as any other prisoner on Robbins Island, despite one’s political credentials, is the same disposition that motivates the most powerful figure in contemporary Christianity to eschew the traditional papal mode of transport—a shiny, spanking new Mercedes Benz—in favor of a 1984 Renault 4 economy car with over 186,000 miles to its name. Humility that accepts a sentence of life imprisonment with an almost cheerful resolve, including the capacity to forgive and befriend one’s captors. Humility that foreswears temptations to hold on to power—and instead gives that power away. Humility that goes out into the streets where the poor are, finding there the wealth of God’s kingdom.

Such humility doesn’t just grow on trees: I don’t see it often in today’s public figures or in the recesses of my own heart. But such humility seems in keeping with the pattern of One who, thinking equality with the Father not to be grasped, took on human flesh, humbling Himself on a cross (Philippians 2).

There may be plenty of other similarities between Nelson Mandela and Pope Francis; but this one, humility, seems to live up to its name: it is, I suspect, the single, most important defining mark of human greatness—and the easiest to overlook. But, what do you think? Are there other commonalities that unite these two men in greatness?