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.
enthymeme (The informal method of reasoning typical of rhetorical discourse. A truncated syllogism.)
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.)
Related Topics of Invention
Almost all of the topics of invention emphasize a logical appeal. There are a few, however, more explicitly associated with the processes of reasoning: