<p>Any cat owner knows the feeling: your cat looks right through you like you're a stranger who happens to operate the food dish. According to the Alphabet of Ben Sira, composed between 700 and 1000 CE, there's an ancient reason for this - and it has to do with what cats eat.</p>
<p>Nebuchadnezzar asked Ben Sira a simple question: why can a dog recognize its owner, but a cat can't? Ben Sira's answer draws on a Talmudic teaching from Tractate Horayot (13a): anyone who eats food that a mouse has nibbled on will suffer memory loss. It was a well-known folk belief in the rabbinic world - mice carried forgetfulness in their teeth, essentially.</p>
<p>Ben Sira takes this principle and applies it with devastating logic. If merely eating bread that a mouse touched causes you to forget your studies, then a cat - who devours the entire mouse, body and all - should lose far more of its memory. The cat eats the concentrated source of forgetfulness itself. No wonder it can't remember who feeds it.</p>
<p>It's a perfect example of the rabbinic reasoning method called kal va-chomer - an argument from lesser to greater. If a small exposure causes a small effect, then a massive exposure must cause a massive effect. The humor comes from applying this perfectly serious logical tool to explain why your cat ignores you. The Alphabet of Ben Sira loves doing exactly this: using the forms of rabbinic wisdom to explain the absurdities of everyday life.</p>