Usage questions, Chicago style

The Chicago Manual of Style's monthly Q&A -- free to all, unlike the online stylebook itself -- can be pretty editor-geeky, all indexing minutiae, en dashes, and footnote options. But CMOS gets some everyday usage questions, too, and the bulletin's editor, Carol Fisher Saller, makes the most of them. A couple (excerpted) from the latest number:

Q.  I have been tutored that because is used for instances of cause/effect and that since is for time. However, one of my authors is a scholar who contends that "since denotes a state of being based on a relationship ... Because implies causality."

A. You and your author seem to be following variations on an old superstition ... Some writers erroneously believe that the word relates exclusively to time. But the causal since was a part of the English language before Chaucer wrote in the fourteenth century.

Q. Is it necessary to use a comma after words like next, then, after that, last, and finally when they are the beginning of a sentence? I am a lower-school teacher and need to clarify this.

A. Punctuation is not so simple that you can make a rule that a comma “always” follows a given word or phrase. Commas depend on syntax as well as pacing, tone, and personal preference ...Please don’t teach your students punctuation until you understand this.

Q. In a sentence, a colon should always be preceded by an independent clause. Why doesn’t the Chicago Manual state this explicitly?

A. Because we’re a bunch of spineless and ineffectual prevaricators -- or because there are times when a colon need not be preceded by an independent clause? A case in point: this one.

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