Reposted by Lennart Ackermans
New: Journal of Mathematical Philosophy
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New: Journal of Mathematical Philosophy - Daily Nous
The Journal of Mathematical Philosophy is a new open-access journal. According to an announcement from its editors, the journal is "the first open access journal that is devoted to mathematical philos...
![Theorem. If $n$ is an integer and $n^2$ is even, then $n$ is itself even.
Proof. Contrapositives are for cowards, so assume $n$ is an integer and $n^2$ is even. Then $n^2=2k$ for some integer $k$, and thus $n^2-2k=0$. Behold:
\[ n = n + (n^2-2k) = n(n+1)-2k. \]
Both $n(n+1)$ and $2k$ are even, so $n$ is even.
QED.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:4wrxafbsjycxbpjo4e42ht6q/bafkreihucnue4bdyzulcrzddytan5ttdx56rg5ci6cn4vhxw5lebnbdzma)