I like the (English) syntax of the article. It seems to have the same concise feeling as the language itself. I like to think that's why pg chooses falsity over falsehood.

It's a little strange to have (id 'a) return nil. Also having car and cdr as historical holdouts when most of the naming seems to aim at an ahistorical stylistic.

Not very deep remarks, since I would need more time to digest.