RhetoricThe Rhetorical SituationRI.9-10.6

Logos: The Reasoning

Logos persuades through the argument itself: evidence, examples and reasoning that show a claim is true or likely.

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The third of Aristotle’s proofs, after pathos and ethos, is logos: persuasion through the argument itself. Aristotle gave it the central place. He called the enthymeme, a short argument that starts from what the audience already accepts and often leaves a step unsaid, the body of persuasion. His other tool was the example: reasoning from a similar case.

Logos includes evidence (facts, numbers, examples, expert findings) and the reasoning that connects it to the claim. An enthymeme: “Students need sleep, and a 7:15 start cuts their sleep, so we should start later.” The unstated step, that schools should protect what students need, is one most listeners already accept.

Key idea

Logos persuades through reasons and evidence that show a claim is true or likely. A fact becomes logos only when the reasoning shows what it proves.

Why it works

Feelings fade and reputations can be questioned, but a clear chain of reasons can be checked by anyone. A reader who follows your reasoning can repeat it to someone else; that is how arguments spread.

Worked example: Logos in the Federalist

In Federalist No. 51 (1788): “If men were angels, no government would be necessary. If angels were to govern men, neither external nor internal controls on government would be necessary.” Where is the reasoning?
  1. Unstated premise: people are not angels. Every reader accepts it.
  2. So government is necessary, to control the governed.
  3. And since the people who govern are not angels either, government must also be controlled.
  4. The famous sentences are an enthymeme: two conditionals and a premise the audience supplies.

Answer: It is logos: a compact argument whose missing premise the reader fills in.

Worked example: A number without context

A flyer says: “Bike crashes on Oak Street doubled this year!” Is that strong logos?
  1. Ask: doubled from what? From 1 to 2 is a very different story from 40 to 80.
  2. Ask: compared to what? If twice as many people now bike on Oak Street, the rate per rider may not have changed.
  3. A number is evidence only when the reader can see what it measures and what it is compared with.

Answer: Not yet. It needs the counts, the time span and a comparison before it proves anything.

Common mistake

Calling any number logos. A frightening statistic dropped in without context mostly works on the reader’s fear, which is pathos, and it can mislead. Check every number: what does it count, out of how many, over what time, and compared with what? Then add a sentence that says what the number shows.
The enthymeme about start times, drawn as an argument. The warrant is the step speakers often leave unsaid (more in The Toulmin Model).
The Logic Ladder teaches the reasoning under logos: premises and conclusions and unstated premises.

Practice

Pass with 3 right answers, the last 2 in a row. Each right answer earns 2 XP.

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Sources and further reading

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