ratiocinatio(n) (rhetoric)

Glossary of Grammatical and Rhetorical Terms

Statue of Roman statesman, philosopher, and rhetorician Marcus Tullius Cicero (106 BC-43 BC) in Rome, Italy. (Paolo Gaetano/Getty Images)


In rhetoric, ratiocinatio is a method of reasoning by which a speaker or writer makes probable inferences about how things are or how things could have been in the past. This method of reasoning commonly takes the form of a syllogism or an enthymeme. Also called syllogismus.

The English word ratiocination (the act of reasoning or a reasoned train of thought) is broadly equivalent to the Latin term (ratiocinatio) used in Roman rhetoric.

The syllogistic reasoning associated with ratiocinatio is a type of logos or logical proof. In his study of Augustine's "styles of proof" and "application of logical principles," theologian Lewis Ayres observes that these "bear closest relation to what the rhetorical handbooks term argumenta, argued by means of ratiocinatio, and having their force not through grand or emotional rhetorical flourishes, but through the power of rational argument" (Augustine and the Trinity, 2010).

See Examples and Observations below. Also see:

Examples and Observations

  • "The method of ratiocinatio was considered by classical rhetoricians to be artificial evidence that, in contrast to non-artificial evidence using witness testimony, created its proofs only through rhetoric. . . . Proof established through ratiocinatio owed its strength to reason."
    (Benjamin Straumann, Roman Law in the State of Nature. Cambridge University Press, 2015)
  • Two Types of Ratiocinatio
    "The status of ratiocinatio . . . [applies] to those cases which are not envisaged by the current law or for which a specific rule is lacking, and which consequently need to be treated by analogy, with the aid of syllogistic reasoning. In discussing this status, Quintilian distinguishes two principal types, the first concerning cases for which there is a partially pertinent norm, and it is possible to infer what is uncertain from what is certain, the second concerning cases for which a law is totally lacking, and it is therefore necessary to resort to another, analogous law."
    (Emmanuel Berti, "Law in Declamation." Law and Ethics in Greek and Roman Declamation, ed. by Eugenio Amato et al. Walter de Gruyter, 2015)
  • Cicero on the Parts of Ratiocinatio
    "[In De Inventione] Cicero considers at length how many parts a ratiocinatio has. Although he is here discussing what in Greek were called enthymemes and syllogisms, he does not use those terms; it is his practice to find a suitable Latin word wherever possible. His own view (1.67) is that ratiocinatio in full form has five parts (what in Greek is called epicheirema): proposition, reason, assumption, reason for the assumption, and conclusion; at a minimum in Cicero's theory (not in his practice, where two-part enthymemes are frequent) it must have at least three parts: major premise, minor premise, and conclusion."
    (George A. Kennedy, Classical Rhetoric and Its Christian and Secular Tradition From Ancient to Modern Times, 2nd ed. University of North Carolina Press, 1999)
  • Ratiocinatio in Paul's Second Epistle to the Corinthians
    In his monograph Ancient Rhetoric and Paul's Apology (2004), Professor Fredrick J. Long observes how a passage from Paul's Second Epistle to the Corinthians "adheres well to Cicero's ratiocinatio." This passage from Paul's letter is followed by an excerpt from Long's analysis. 

    - "Now it is not necessary for me to write to you about the ministry to the saints, for I know your eagerness, which is the subject of my boasting about you to the people of Macedonia, saying that Achaia has been ready since last year: and your zeal has stirred up most of them. But I am sending the brothers in order that our boasting about you may not prove to have been empty in this case, so that you may be ready, as I said you would be; otherwise, if some Macedonians come with me and find that you are not ready, we would be humiliated --to say nothing of you--in this undertaking. So I thought it necessary to urge the brothers to go on ahead to you, and arrange in advance for this bountiful gift that you have promised, so that it may be ready as a voluntary gift and not as extortion."
    (Paul, Second Corinthians 9:1-5. The New Revised Standard Version of the Bible, Catholic Edition)

    - "Paul was working from premises (9.1,3) towards a conclusion (9.5). His argument is that his sending of the brethren to prepare for the collection (minor premise) in no way should impede the Corinthians' eagerness to contribute to the collection (major premise). Paul preserved the dignity of the Corinthians by first affirming the premise that the Corinthians are eager to contribute to the collection. . . . The argument in 9.1-5 flows to the next argument in 9.6-16, which expounds the rationale for the Corinthians to give 'bountifully' (9.6) based upon the abundance of God's grace."
    (Fredrick J. Long, Ancient Rhetoric and Paul's Apology: The Compositional Unity of 2 Corinthians. Cambridge University Press, 2004)
  • Quintilian on Ratiocinatio and Emphasis
    "In order to make clear how ratiocinatio should be understood Quintilian relates this phenomenon to the rhetorical concept of emphasis: 'This form of amplification is near akin to emphasis: but emphasis draws its effect from the actual words, while in this case the effect is produced by inference from the facts, and is consequently far more impressive, inasmuch that facts are more impressive than words.' Common to ratiocinatio and emphasis is that both emphasize and stress the content exclusively by hinting at something. The difference is that Quintilian connects ratiocinatio to facts that hint at something beyond themselves, while emphasis is concerned with words or expressions that mean more than they say. Not all rhetoricians make this distinction . . .."
    (Ivar Vegge, Second Corinthians, a Letter About Reconciliation. Mohr Siebeck, 2008)