Q. How should one handle mentions of questions, rather than direct expressions of them? As an example, consider this sentence: The question “What is dark energy?” has been a major focus of cosmology for decades. Should there be a comma after “question”? Should the question be set within quotation marks? Should it instead be set in italics? Is there some other format that Chicago would recommend?
A. When a question occurs within another sentence—but not as a form of direct discourse introduced with a verb like asked or wondered—it can usually be treated like any other noun. Whether to use a comma in your example will depend, then, on whether the question itself is restrictive or nonrestrictrive relative to the word question.
If you don’t know what that means, consider these two sentences (and see CMOS 6.30):
The artist Frida Kahlo has been a major focus of self-portraiture studies for decades.
The question What is dark energy? has been a major focus of cosmology for decades.
Just as “Frida Kahlo” is essential to the meaning of the word artist in the first sentence, “What is dark energy?” is essential to the meaning of the word question in the second. In other words, the name and the question are both restrictive, so no commas are needed in either sentence.
If the artist or question has already been introduced, or if either one is preceded by a limiting adjective like this (see also CMOS 5.72)—or if both are true—those same elements become nonrestrictive and are set off by commas. For example:
We were discussing a question that, to date, has no definitive answer. This question, What is dark energy?, has been a major focus of cosmology for decades.
Quotation marks are usually unnecessary for such questions unless you’re quoting someone or something directly. And though italics can be helpful, they aren’t usually necessary either. For the use of a comma following a question mark (which you could avoid in the example above by using dashes or parentheses instead), see CMOS 6.134. For commas with direct questions (with asked or the like), see 6.45.