Monday, May 3, 2010

Fact-checking and evaluating logic in information sources

Whenever you evaluate an information source, you should not only check it for timeliness, reliability, authority, and perspective (see last week's post) but also for factual correctness and strong logical arguments.

To check facts, go to a known and reputable reference source. The Library provides access to hundreds of high quality online reference materials through
You can also check facts against other reliable sources like your textbooks.

Checking the logic of a source's arguments is a little more difficult. There are dozens of kinds of logical errors that an author can make, and some of them appear to make sense, at least if you're not paying close attention.

Some common types of logic errors, or fallacies are:
  • appeal to authority - "Aristotle said the sun revolved around the earth, and Aristotle was very wise, so he must be correct."
  • ad hominem attack - "In the early 20th century, the medical industry conducted experiments on minorities, so you can't trust doctors when they say that swine flu is caused by the H1N1 virus and not by a government plot."
  • appeal to ignorance - "I can't imagine what else those helicopters could be doing, so they must be spying on citizens."
  • circular argument - "The oracle says she speaks God's word, so we can't question the Oracle."
  • appeal to consequences - "If you believe that human beings evolved from a common ancestor with apes, then you believe that human beings are animals, so you don't believe in human rights."
  • appeal to popularity - "Everybody knows that the more powerful a computer is, the bigger it is." (Everybody did think they knew this back in the 1960s.)
  • sample bias - "99% of survey respondents say second-hand smoke doesn't cause health problems." (If your survey respondents all work for the tobacco industry, you might get that result.)
  • begging the question - "When children are possessed by frog demons, they show symptoms that mimic common childhood ailments."
You get the picture. This website is an excellent place to learn about different logical fallacies and confirm whether you've spotted one "in the wild": LogicalFallacies.info


Empire State College Library Research Blog
Questions? Ask a Librarian

No comments: