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  "body": "\n## Statement\n\nFor all natural numbers $a$ and $b$, $a + b = b + a$.\nHere $+$ is the [[addition of natural numbers|0W5DSDFQ4G]].\n\n## Remarks\n\nThe proof from the recursive definition of addition uses the [[principle of mathematical induction|0ASJVEFA9J]] two times.\nAn operation $\\ast$ on a set is commutative when $x \\ast y = y \\ast x$ for all $x$ and $y$. Multiplication of natural numbers is also commutative.\nSubtraction of integers is not commutative: $3 - 1 \\neq 1 - 3$.\n\n## Explanations\n\n### L1 human\n\nThe order of two numbers in a sum does not change the result: $2 + 5$ and $5 + 2$ are both $7$.\nThink of two piles of stones: you count the same total when you count the second pile first.\n",
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