Though best known as a poet and short story writer, Edgar Allan Poe was also a notable editor and critic. (See, for instance, Poe's New York in the 1840s.) In a short article in the February 1848 issue of Graham's Magazine, he offered these thoughts on the rhetorical power of punctuation:
That punctuation is important all agree; but how few comprehend the extent of its importance! The writer who neglects punctuation, or mix-punctuates, is liable to be misunderstood--this, according to the popular idea, is the sum of the evils arising from heedlessness or ignorance. It does not seem to be known that, even where the sense is perfectly clear, a sentence may be deprived of half its force--its spirit--its point--by improper punctuation. For the want of merely a comma, it often occurs that an axiom appears a paradox, or that a sarcasm is converted into a sermonoid.Unfortunately, Poe (who died in 1849) never got around to composing his treatise. But he did have a few words to say in defense of an often maligned mark of punctuation--the dash:
There is no treatise on the topic--and there is no topic on which a treatise is more needed. There seems to exist a vulgar notion that the subject is one of pure conventionality, and cannot be brought within the limits of intelligible and consistent rule. And yet, if fairly looked in the face, the whole matter is so plain that its rationale may be read as we run. If not anticipated, I shall, hereafter, make an attempt at a magazine paper on "The Philosophy of Point."
Every writer for the press, who has any sense of the accurate, must have been frequently mortified and vexed at the distortion of his sentences by the printer's now general substitution of a semicolon, or comma, for the dash of the MS. The total or nearly total disuse of the latter point, has been brought about by the revulsion consequent upon its excessive employment about twenty years ago. The Byronic poets were all dash. . . .
Without entering now into the why, let me observe that the printer may always ascertain when the dash of the MS. is properly and when improperly employed, by bearing in mind that this point represents a second thought--an emendation. In using it just above I have exemplified its use. The words "an emendation" are, speaking with reference to grammatical construction, put in apposition with the words "a second thought." Having written these latter words, I reflected whether it would not be possible to render their meaning more distinct by certain other words. Now, instead of erasing the phrase "a second thought," which is of some use--which partially conveys the idea intended--which advances me a step toward my full purpose--I suffer it to remain, and merely put a dash between it and the phrase "an emendation." The dash gives the reader a choice between two, or among three or more expressions, one of which may be more forcible than another, but all of which help out the idea. It stands, in general, for these words--"or, to make my meaning more distinct." This force it has--and this force no other point can have; since all other points have well-understood uses quite different from this. Therefore, the dash cannot be dispensed with.
It has its phases--its variation of the force described; but the one principle--that of second thought or emendation--will be found at the bottom of all.
In our own time, many still view the dash with suspicion. As Bryan Garner writes in Garner's American Usage (Oxford University Press, 2003), "The em-dash is perhaps the most underused mark in American writing. Whatever the type of writing, dashes can often clarify a sentence that is clogged up with commas--or even one that's otherwise lusterless."
To learn more about the dash (and other neglected or abused marks of punctuation), visit Semicolons, Colons, and Dashes.