John Quincy Adams, answered from the texts and cited to the page.
The word has been so thoroughly captured by the modern English usage that I must begin by rescuing it from that capture before I can say anything useful about it. Sheridan, Walker, and the modern English writers on the subject use elocution to mean the act of speaking — the delivery, the voice, the manner of utterance.1 That is precisely what the ancient rhetoricians called pronunciation, or action; and the confusion between these terms is not a pedantic matter, because it collapses two entirely distinct operations of the orator's art into one word, and leaves the other operation nameless.2
In the ancient sense, which is the sense I employ in the Lectures on Rhetoric and Oratory — the course I delivered at Harvard beginning in 1806 — elocution refers to the writer, not to the speaker; to the diction, not to the delivery.3 Cicero's definition, which I adopted at the commencement of the course, puts it with precision: elocution is the application of proper words and sentences to the materials of invention.4
Invention furnishes the matter; disposition furnishes the order; and elocution furnishes the manner — the clothing of the thoughts with language.5 It is the act, not of the voice, but of the pen; and a discourse which was never spoken may have good or bad elocution as surely as one delivered before the largest assembly.6 I have observed to students that when they sit down to write upon any assigned topic, they are far more often at a loss for the combining and arranging hand of art than for the thoughts themselves.7
That is the province of elocution: to take what invention has discovered and what disposition has ordered, and to give it the words in which it can do its work. Under that head fall elegance, composition, and dignity — though even these three terms require careful unpacking, since their combination, as it first appears, seems an incongruous assembly: elegance and dignity are properties of the work, while composition is the act of the workman, and they do not all belong to the same logical category without explanation. Memory — the firm possession and ready command in the mind of the thoughts, arrangement, and words into which the discourse has been reduced — follows elocution in the ancient division.8
And pronunciation, or action, which the modern world has taken to calling elocution, comes last: the delivery of the discourse by speech, encompassing both the voice and the gesture in their combination.910 The reason I insist on the ancient sense, rather than accommodating the modern one, is this: those of you for whom the science has a particular interest will naturally return to the ancient fountains, and you cannot read Cicero or Quintilian without knowing that they always annex to the word this signification.11
A student who has been taught that elocution means delivery will find everything those masters say upon the subject absurd or unintelligible — which is precisely the confusion a course of instruction is meant to prevent.
Sheridan, Walker, and others, who have published professed treatises upon elocution, mean by that word the mode of speaking, or delivery; the same thing, which by the ancients was understood under the name of action.Lectures on Rhetoric and Oratory, Vol 2
Here, and among all the ancient rhetoricians and orators, pronunciation and action are used indiscriminately to signify that, which consists of their combination; that is, delivery.Lectures on Rhetoric and Oratory, Vol 1
But in the language of Cicero and Quinctilian elocution refers to the writer, and not to the speaker; to the diction, and not to the delivery.Lectures on Rhetoric and Oratory, Vol 2
Elocution, as the application of proper words and sentences to the materials of invention.Lectures on Rhetoric and Oratory, Vol 2
In terms still more concise invention may be said to furnish the matter, disposition the order, and elocution the manner, for the composition of a public discourse.Lectures on Rhetoric and Oratory, Vol 2
It is the act, not of the voice, but of the pen. It is the clothing of the thoughts with language; and applies to all written compositions. So that the elocution may be good or bad, of a discourse, which never was spoken, as much as of one, that was.Lectures on Rhetoric and Oratory, Vol 1
When called to write upon any topic, assigned you, I presume you have often been much more at a loss how to combine and arrange your thoughts, than for the thoughts themselves; and often wanted more the disposing hand of art, than the genial fertility of nature.Lectures on Rhetoric and Oratory, Vol 1
Elegance and dignity may be conceived, as qualities of composition. They are merely the properties of the work. Composition is the act of the workman. The three specific constituent expressions do not belong to the same general term.Lectures on Rhetoric and Oratory, Vol 2
Memory is the firm possession and ready command in the mind of the thoughts, arrangement, and words, into which the discourse has been reduced.Lectures on Rhetoric and Oratory, Vol 1
Pronunciation is the delivery of the discourse by speech. It is also called action; and, as I have already observed, is the same thing, which, in ordinary acceptation, and by the modern English oratorical writers, is called elocution.Lectures on Rhetoric and Oratory, Vol 1
as you never can understand Cicero and Quinctilian without first knowing, that they always annex to the word this signification; and as the rules of this institution prescribe the consideration of this subject under that meaning; I have thought best not to discard it, but to explain to you so explicitly the sense, in which I am to employ the expression.Lectures on Rhetoric and Oratory, Vol 1