Mrs. Farrow had been retired for four years when the letter arrived.
It was from a student she barely remembered — Thomas something, 2007 or 2008, one of maybe twenty-five faces in the Tuesday afternoon class. He had gone on to become a civil engineer. He was writing because, he said, he'd been thinking about something she'd told his class, and he wanted her to know it had mattered.
She had taught secondary mathematics for thirty-one years. She could not remember what she'd told any particular class on any particular day.
Thomas described it precisely: she had been explaining how to read a graph, and she'd said that numbers were not the thing itself, they were a description of the thing, and the description was always a simplification, and the skill was in knowing what was simplified out and whether it mattered. She'd moved on quickly and he'd remembered it for sixteen years.
Mrs. Farrow read the letter twice. She had no memory of saying it. She probably had said it — it sounded like something she'd say. But the version Thomas remembered was more elegant than anything she could reconstruct. He'd taken what she'd said and improved it in the keeping.
She wrote back: thank you, and I'm glad it mattered, and you improved it — the version you remember is better than anything I would have written down.
What she didn't say: I have said perhaps a hundred thousand things to students over thirty-one years, and I know the outcome of almost none of them. You're the seventeenth person to write. Each one was a surprise. I had given up expecting to know.
She had given up expecting to know, and then the letter arrived, and she went through the rest of the day differently.