EPICHEIREMA

The word epicheirema comes from the Greek “epicheirein, meaning « to endeavor, attempt to prove » (Webster, epicheirema). It  is translated into Latin as ratiocinatio (Cicero), meaning “reasoning”, or as argumentatio (Ad. Her.) meaning « argument. »

In ancient argumentation theory, the term epicheirema has three different definitions.

1. The epicheirema as dialectical reasoning

The Aristotelian theory of syllogistic reasoning contrasts the philosopheme with the epicheirema. A philosopheme is another name for an analytical or scientific syllogism, in which the premises are true and the rule of deduction is valid (Top., VIII, 11; p. 156).
In contrast, an epicheirema is a dialectical inference” (ibid.), that is, a syllogism based on premises taken from the doxa, and, therefore only probable. This inference leads to a probability.

2. The epicheirema as an argumentation whose premises are themselves argued.

In rhetorical argumentation, the word epicheirema is a synonym for probable (rhetorical) syllogism, enthymeme and argumentation. A well-constructed, persuasive, rhetorical proof is defined as an argument (ratiocinatio) whose premises are only probable, and should therefore be explicitly supported by proofs (Cicero, Inv. I, 34; Hubbell, pp. 98-99).
In short, a probable premise becomes certain when it is  accompanied by its proof. Cicero discusses the following rhetorical syllogism (id., 101-103)

— Premise 1 + proof of premise 1:

Premise 1: “Things that are governed by design are managed better than those that are not.”
Proof of premise 1: “A house that is managed in accordance with a reasoned plan is better managed that those that are not. The army […] The ship […]”

— Premise 2 + Proof of Premise 2:

Premise 2: “Of all things, the universe is best governed.”
Proof of Premise 2 (our numbering and presentation)
(a) “The rising and the setting of the constellations follow a fixed order.”
(b) “The changes of the seasons not only (b1) proceed in the same way by a fixed law but (b2) are also adapted to the advantage of all nature.
(c) “The alternation of night and day has never caused any harm through variation.”

— Conclusion: “Therefore, the universe is governed by design.”

Premise 1 is the conclusion of an induction, that is, an enumeration of examples, that have the same structure and orientation.
In premise 2, case (b), the element (b2) argues for not only a design but also for a benevolent design, as does case (c).

Structure of an epicheirema
Whether an epicheirema consists of five or three components is a controversial question (Solmsen 1941, p. 170). On the surface level, an epicheirema is a sequence of five components:

Premise 1 + Proof of Premise 1 + Premise 2 + Proof of Premise 2 + Conclusion.

This corresponds to a three-element deep structure:

(Premise 1 and its proof) + (Premise 2 and its proof) + Conclusion

This is Quintilian’s position: “To me, as well as to the majority of authors, there appear to be no more than three [parts]” (IO, V, 14, 6).

The epicheirema corresponds to a linked argument, presented as follows:

3. The epicheirema is a communicated argument

The Rhetoric to Herennius defines

The most complete and perfect argument [argumentatio]” as “that which consists of five parts: the proposition, the reason, the proof of the reason, the embellishment and the résumé.  (Ad Her., II, 28)

This perfect rhetorical argument is described as a sequence of five components, similar to a logical epicheirema, but with a completely different organization.

Logical component
The first three elements correspond to the linear development of the argument  that establishes the proposition:

[Reason 1 + Proof of the Reason] + Proposition

The proof of the reason, “corroborates the briefly presented reason by means of additional arguments” (Id., p. 107). The overall argument must now be viewed as serial:

[Argument₁   =>       {(Conclusion] = Argument₂)    =>  Conclusion}
Proof of the Reason                    Reason                                Claim

Communicative component
The embellishment is a reformulation that “adorns and enriches the argument (argumentatio).” The concluding résumé is not the conclusion. Its “[brevity]” contrasts with the preceding episode of amplification episode, creating a kind of hot / cold contrast. This component of the argumentation articulates two elements that clearly have a communicative function.

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