In What Language Is, linguist John McWhorter investigates the tongue-twisting complexities of language.

You spotlight the fiendishly complex Caucasian language called Archi, with its one million verb forms. Why do they need so many?

They don't. Most languages spoken by a few thousand people are so complicated they make your head swim; a Siberian yak herder's language is much more complicated than a Manhattan bond trader's. Languages develop complexity from entrenched habits. First comes a word meaning "more than one," like "bunch." People start using it for "more than one" of everything, it shortens to one sound and becomes a suffix like the English plural "s." Multiply that by 10,000 things, and you get needless complication.

You also examine how languages become simpler by comparing African-American dialect to Hebrew.

Black English is simpler than Standard English in some ways; for example, it often gets by with just "be" and drops "am," "is," and "are." That's because Black English arose when adult African slaves learned the language. Children are incredibly good at learning complexities and irregularities, but adults are not; when adult Africans came here and learned English, some complexities fell away. Similarly, modern Hebrew was revived by adults in Israel, so complex aspects of biblical Hebrew got shaved down. People think of Black English as ungrammatical, but it bears the same relationship to Standard English as contemporary Hebrew does to ancient Hebrew.

You're both a linguist and a prolific writer. Does one influence the other?

As a linguist I see the arbitrariness of strictures editors force on me as a writer. A lot of the things they fix in my prose are not a matter of grace or logic; it's just what they're getting from Strunk and White—much of which is utter nonsense. Take singular "they," as in "each student can come upstairs when they finish their exam." We're always told "they" is plural, but it's been singular in earlier stages of English. "His or her" is absurd, alternating "he" and "she" is awkward—sometimes you need a good "they." So I use it; it's not improper, and I should not get mail correcting me on it (which I do).

Should we take a more relaxed view of language?

I like to watch the changing lump in the lava lamp. I've noticed that students are starting to talk about things being "based off of" something. A typical person, who hears new things as scourges, as youth-speak, as illogical, might say "That's not correct—it should be ‘based on.' " But to me, there's just a new expression, "based off of," that's becoming more prevalent. I wish people would join me in seeing language as a chaotic, growing garden.