The gratitude of the heart is the only debt which increases the more we pay it.
He names a kind of arithmetic that defies banks. The more you return kindness, the richer everyone becomes. It explains his quiet miracle for the Morrels and why he hides his hand—pure gifts don’t ask to be seen. Emotionally, the line lifts the chest; we want to live like that. It’s a counter-creed to revenge math. The novel balances both ledgers, then chooses this one to end on.