John Quincy Adams spent part of his life as a professor; he was professor of logic for a while at Brown University, and then accepted the Boylston Professorship of Rhetoric and Oratory at Harvard. It was a subject he was eminently qualified to teach, having both a thorough mastery of all the classical and modern works on the subject as well as a practical familiarity with the art itself, and, perhaps, just as importantly, a passionate belief in the importance of rhetoric to the survival and prosperity of a republic. President Madison asked him to be the first ambassador to Russia, and so after only a few years he resigned his professorship, but he was asked by his colleagues to publish his popular lectures, which he did, in 1810, under the title, Lectures on Rhetoric and Oratory.
The lectures have much of interest in them, especially on the subject of figurative language, which he discusses at length. Adams has an associationist account of figurative tropes. As he conceives it, every figure of speech involves three elements of meaning -- the literal sense, which serves as a kind of reference point, another idea which one intends to convey, and a "chain of communication" between the two ideas, consisting of some association of imagination. On the basis of this assumption, he is able to give a coherent account of the traditional four major tropes (Volume 2, p. 311):
There are four distinct principles of association so familiar to the minds of men, that they serve as the foundations, upon which the use of a word, meaning one thing, for a thought meaning another, is justified in the practice of all nations. The first of these is similitude; the second, the relation between cause and effect; the third, the relation between a whole and its parts; and the fourth is opposition. These various relations form the connecting links of all the principal tropes. Hence it has been contended, that there are only four primary tropes; the metaphor, founded upon similitude; the metonomy, founded upon the relation between cause and effect; the synecdoche, standing on the relation between a whole and its parts; and irony, the basis of which is opposition. There are however various other distinctions, which the continual analytic process of theory has discovered, which form a secondary class of tropes.
This is fairly similar to Hume's list of principles of association -- resemblance, causation, contiguity -- especially when one adds the principle Beattie added in critiquing Hume, contrariety. I don't know that there is a direct influence here. Beattie had already remarked that Hume's principles of association were already discussed in the context of memory by Aristotle (in the De memoria), and all of these people read the same classical sources. On the other hand, Adams was extremely familiar with Hume, who also has an associationist account of figurative language (although not one developed in precise detail), so a direct influence can't be ruled out, either.
Adams says a number of other interesting things about figurative language. One of his particularly interesting ideas, which I think deserving of more consideration, is that figurative language has a quasi-synaesthesic character (which Beattie also notes). "The purpose of figurative speech," he says (p. 269), "is to address the eye through the medium of imagination." Hearing is a relatively impoverished sense, considered in itself; it receives sounds, but these sounds must be interpreted as signs to be of any use. However, because these signs are associated with other sensory phenomena in our imagination, the clever orator can make use of them to conjure up other sensory details in the minds of his audience. "Every image, under which a writer or speaker proposes to display thought, is a picture" (p. 274), and for this reason Adams recommends his students always test out their figures of speech by considering how they would seem if painted on a canvas -- because our sense of the quality of the figure of speech can be easily distorted by other things (e.g., familiarity), and a figure of speech is so often using sounds to encourage a picturesque vision in the imagination.
Adams often displays a sense of humor in his handling of his material. The best of his jokes is that with which he introduces irony (p. 340):
Perhaps of all the figures of speech, that, which would least require an explanation, is the irony; which is so convenient an instrument of that mutual benevolence, which mankind are delighted to extend to one another, that I question whether there was ever a student, who had made the proficiency necessary for obtaining admission within these walls, but understood its character, as well as any of his teachers.
Various Links of Note
* P. S. Ruckman, Jr. looks back at problems in the Obama Administration's approach to clemency.
* Some of the history of the persecution of Copts in Egypt.
* The history of the Comic Sans typeface.
* Alex Good, The Rising Tide of Educated Aliteracy
Christ Our Pascha
Donald Ainslie, Hume's True Scepticism
Mark Anderson, Pure: Modernity, Philosophy, and the One
Michael Flynn, Eifelheim