The term expression is used in Aristotelian rhetorical theory and critical theory with three quite distinct meanings.
1. A language-related paralogism
In the Sophistical Refutations, the label “paralogisms of expression” covers the six paralogisms “related to language”:
Homonymy Composition Accent
Amphiboly Division Expression. S. Fallacy (2): Aristotle foundational list.
This label can also be used to specifically refer to the paralogism of homonymy.
A speech is said to be fallacious by expression when although expressed formally as a demonstration, it has no demonstrative content. The speech may take the form of a demonstration, if, for example the speaker introduces a high number of argumentative indicators. When there is no semantic connection between the connected propositions A and B, the argument “A, therefore B” is said to be fallacious due to the “form of the expression”. The conclusion is drawn “although there has been no syllogistic process” (Rhet., II, 24, 1401a1; Freese, p. 325), that is without any real argumentation.
Such examples can sometimes be found in academic essays overloaded with argument indicators, hoping that they will end up producing an argument. The discourse of Pangloss, railed at by Voltaire in Candide, is of that kind:
[After the earthquake that ravaged Lisbon]
Some [citizens] whom they had succored, gave them as good a dinner as they could in such disastrous circumstances; true, the repast was mournful, and the company moistened their bread with tears; but Pangloss consoled them, assuring them that things could not be otherwise. “For,” said he, “all that is for the best. If there is a volcano in Lisbon it cannot be elsewhere. It is impossible that things should be other than they are; for everything is right.
Voltaire, Candide, or The Optimism. .
3. Misleading expressions
In Aristotle Sophistical Refutations, the fallacy of “form of expression” is also called the fallacy of “form of discourse”, as well as a “figure of discourse”, a label likely to introduce formidable confusions. The fallacy of form of expression corresponds exactly to the phenomenon that analytic philosophers discuss under the heading of misleading expressions.
For example, according to Ryle, a statement such as “Jones hates the thought of going to hospital” (1932, p. 161) suggests that the phrase “the thought of going to hospital” refers to some existing object, its reference; this expression induces a belief in the existence of “‘ideas’, ‘conceptions’, ‘thoughts’ or ‘judgments’” (ibid.). Ryle considers that to eliminate such non-existing entities, the statement must be rewritten in the form corresponding to its semantic-ontological reality: “Jones feels distressed when he thinks of what he will undergo if he goes to hospital” (ibid.). This new formulation is not supposed to contain any reference to deceptive entities such as “the idea of going to hospital” (ibid.).
Analytical philosophy has devoted substantial efforts to the study of misleading expressions as expressions that generate non-existent problems, as seen in the previous case, or expressions which are superficially similar but whose semantic structure is very different, as shown by the following examples.
— According to Austin’s analysis (), descriptive statements and performative statements have the same superficial grammatical structure, whilst their meanings and references are very different. The former refer to states of the world, whereas the latter produce the reality they formulate.
— The words “the path is stony and steep” and “the flag is red and black” are syntactically analogous, yet one can infer from the first that “the path is stony” and that “the path is steep” whilst it cannot be inferred from the second that “the flag is red” and that “the flag is black”. Fallacies of composition and division can be considered as a particular case of fallacious expression by the form of the expression.
— The similarity of superficial linguistic forms, can lead us to attribute to a word an erroneous semantic characterization. For example, suffering and running are syntactically, intransitive verbs, and, from this analogy, one might think that, like running, suffering expresses an action.
— The arguments drawn from derivative words might also be criticized as cases of fallacies of expression, S. Derived Words.
 Quoted after Voltaire, Candide, Chap. V. New York, Boni and Liveright, 1918. No pag. https://archive.org/stream/candide19942gut/19942.txt (11-08-2017)