Figures of logos
The Ancient Rhetoricians believed that a persuasive appeal involved ethos (appeals to the personal credibility of the speaker), logos (appeals to logic or reason) and pathos (appeals to the emotions).
Logos names the appeal to reason. Aristotle wished that all communication could be transacted only through this appeal, but given the weaknesses of humanity, he laments, we must resort to the use of the other two appeals. The Greek term logos is laden with many more meanings than simply "reason," and is in fact the term used for "oration."
Sample Rhetorical Analysis: LOGOS
When Descartes said, "I think; therefore, I am," his statement reflected in its pure concision and simple logical arrangment the kind of thought and being he believed to be most real. He did not claim, as Pascal would later do, that our being has as much to do with feeling as it does thinking. Descartes here equates pure rationality and pure being, persuading us of the accuracy of this equation by the simplicity of his statement. There is no room for the clouds of emotion in this straightforward formula; it makes a purely logical appeal.
Figures of reasoning
Nearly every figure of speech may be used to make an argument more reasonable. However, many figures are specifically designed to appeal to logos, logic, or else are variations upon the parts or processes of formal reasoning. Figures of reasoning, in a legal context, are most commonly applied when presenting a legal argument. They include:
Enthymeme - see Enthymeme under the section on rhetoric
Sorites - a chain of claims and reasons which build upon one another. Concatenated enthymemes.
Syllogismus - the use of a remark or an image which calls upon the audience to draw an obvious conclusion.
Aetiologia- a figure of reasoning by which one attributes a cause for a statement or claim made.
Ratiocinatio-reasoning (typically with oneself) by asking questions.
Anthypophora- a figure of reasoning in which one asks and then immediately answers one's own questions.
Apophasis - the rejection of several reasons why a thing should or should not be done and affirming a single one, considered most valid.
Contrarium-juxtaposing two opposing statements in such a way as to prove the one from the other.
Expeditio-after enumerating all possibilities by which something could have occurred, the speaker eliminates all but one.
Proecthesis- when, in conclusion, a justifying reason is provided.
Prosapodosis- providing a reason for each division of a statement, the reasons usually following the statement in parallel fashion.
Paromologia -admitting a weaker point in order to make a stronger one.
Dirimens copulatio- a figure by which one balances one statement with a contrary, qualifying statement
Commoratio- dwelling on or returning to one's strongest argument.