| Measure | Question | Examples and Notes |
|---|---|---|
| S ufficiency | Is there enough cited evidence to support the conclusion? | Generally, only “strongly” and not “weakly” supported conclusions should be accepted. The more controversial a claim is, the more evidence authors should provide before expecting an audience to accept it. If the evidence is not sufficient, the author may need to modify or qualify the claim, by stating that something is true ‘sometimes’ rather than ‘always’. |
| T ypicality | Is the cited evidence typical or representative? | If an author makes a claim about a whole group but the evidence is based on a small or biased sample of that group, the evidence is not “typical.” Similar problems stem from relying just on personal experiences (anecdotal evidence) and from “cherry picking” data by citing only the parts that support a conclusion while ignoring parts that might challenge it. |
| A ccuracy | Is the cited evidence up to date and accurate? | Authors using polls, studies and statistics must ask whether the data were produced in a biased way and also ask whether the sample was large and representative of its target population so that results were outside the “margin of error.” ( Margin of error : If a sample is too small or not well chosen, results may be meaningless because they may represent random variation.) |
| R elevance | Is the cited evidence directly relevant to the claim(s) it is being used to support? | An author may supply lots of evidence, but the evidence may support something different from what the person is actually claiming. If the evidence is not relevant to the claim, the author may need to modify or qualify the claim—or even to acknowledge that the claim is indefensible. |
Manipulative Appeals to Logos
Diagramming an argument can help you determine if an appeal to logos is manipulative. Are the premises true? Does the conclusion follow logically from the premises? Is there sufficient, typical, accurate, and relevant evidence to support inductive reasoning? Is the speaker or author attempting to divert your attention from the real issues? These are some of the elements you might consider while evaluating an argument for the use of logos.
Pay particular attention to numbers, statistics, findings, and quotes used to support an argument. Be critical of the source and do your own investigation of the “facts.” Maybe you’ve heard or read that half of all marriages in America will end in divorce. It is so often discussed that we assume it must be true. Careful research will show that the original marriage study was flawed, and divorce rates in America have steadily declined since 1985 (Peck, 1993). If there is no scientific evidence, why do we continue to believe it? Part of the reason might be that it supports our idea of the dissolution of the American family.
Study the mapped visualization of crime in the U.S. below and answer the questions about how it appeals to logos.