<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet href="/rss/styles.xsl" type="text/xsl"?><rss version="2.0"><channel><title>Reductio ad Unum</title><description>Essays on mathematics, physics, philosophy, computing, and economics.</description><link>https://reductioadunum.com/</link><item><title>Hello, world</title><link>https://reductioadunum.com/posts/hello-world/</link><guid isPermaLink="true">https://reductioadunum.com/posts/hello-world/</guid><description>What this blog is, how it is built, and how to write for it.</description><pubDate>Sun, 13 Sep 2026 00:00:00 GMT</pubDate><category>computing</category></item><item><title>Why Euler&apos;s identity is not magic</title><link>https://reductioadunum.com/posts/why-euler-identity-is-not-magic/</link><guid isPermaLink="true">https://reductioadunum.com/posts/why-euler-identity-is-not-magic/</guid><description>The most famous equation in mathematics is a corollary of a definition, and that is the interesting part.</description><pubDate>Thu, 10 Sep 2026 00:00:00 GMT</pubDate><category>math-physics</category></item><item><title>The Ship of Theseus in software</title><link>https://reductioadunum.com/posts/ship-of-theseus-in-software/</link><guid isPermaLink="true">https://reductioadunum.com/posts/ship-of-theseus-in-software/</guid><description>Every long-lived codebase has had every line replaced. What, if anything, is the same program?</description><pubDate>Sat, 05 Sep 2026 00:00:00 GMT</pubDate><category>philosophy</category><category>computing</category></item><item><title>The opportunity cost of free</title><link>https://reductioadunum.com/posts/opportunity-cost-of-free/</link><guid isPermaLink="true">https://reductioadunum.com/posts/opportunity-cost-of-free/</guid><description>Zero-price goods still cost something. The price just moved somewhere harder to see.</description><pubDate>Fri, 28 Aug 2026 00:00:00 GMT</pubDate><category>economics</category></item></channel></rss>