But every so often, a child makes a promise that does not fade, that takes root somewhere deeper than memory, that becomes not a thing the child remembers but a thing the child is.

And I have come to think that these unfading promises have a particular power precisely because they were made before the child understood the cost.

When Julian promised his dying sister that he would carry her across his graduation stage, he was five years old, and he did not know what it would cost him.

He did not know about middle-school cruelty, or the terror of adolescent social judgment, or how it would feel to have his own father turn away, or what it is to stand before six hundred laughing people.

He promised in the pure ignorance of a five-year-old, for whom the promise was simply true, simply what you do when your sister is scared and you love her.