Jon,

In your explanations of category theory, you forgot to explain why category theorists tend to confuse Halloween and Christmas.

Isomorphism below.

John

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Category theorists say that if you have an isomorphism between two categories, all  operations on one are equivalent to operations on the other.  For the isomorphism of octal integers and decimal integers, there is a mapping of 31 Oct ↔ 25 Dec.