Lewis Thomas on colons and semi-colons

I like what the wonderful essayist Lewis Thomas has to say about these punctuation marks, and how he distinguishes them.

The semi-colon, which Thomas has "grown fond of," he describes as a reminder that something needs to be added to the sentence. With a semi-colon, he says, "you get a pleasant little feeling of expectancy; there is more to come..."

Colons he finds "far less attractive," since they give the reader a feeling of "being ordered around, or at least having your nose pointed in a direction you might not be inclined to take if left to yourself..."

A further objection to colons is that they point to "sentences that will be labelling the points to be made: firstly, secondly and so forth, with the implication that you haven't enough sense to keep track of a sequence of notions without having them numbered."*

In a more prosaic world than that of the fanciful land of Lewis Thomas, the function of a colon is to indicate a list to come, whether this consists of words or phrases, like this: Tom, Dick and Harry, or like this: Tom's dog, Dick's cat, and Harry's monkey.

On the other hand, semi-colons, unlike mere commas, are permissible when you want to "glue" two independent clauses together. Of course, these clauses should be closely related; otherwise, you would be using a period at the end of the first one and starting a new sentence with the second.

*The quotations come from Thomas's essay "Notes on Punctuation," originally published in 1974 in a lovely collection called The Medusa and the Snail: More Notes of a Biology Watcher (Bantam: New York).

Try a free quiz by Jane Straus on Colons and Semi-colons here.