Informal Logic and Solar Bird Fallacy

Equivocating sounds hard to do, but it isn't. One "equivocates" (say "Ee - KWIV - oh - kayts") when he uses the same word or phrase with a different sense in more than one instance, while pretending or thinking he has used them to convey the same meaning. Here is an example of a syllogism -- a set of propositions and a conclusion that is supposed to follow from them by logical necessity -- that equivocates on the word "light."

1. Feathers are light.
2. The sun gives off light.
3. Therefore, the sun gives off feathers.

Does the sun really give off feathers? Of course not; this is just a bit silly, yes? Then where did this syllogism go wrong? It's time for a little detective work. Get out the magnifying glass.

Proposition one is true, since feathers have a small mass and usually weigh less than other objects with which you might compare them. Proposition two is also true and is easily observable so to be. The "therefore" is the problem here, since the conclusion depends on the word "light" meaning the same thing in proposition one as it does in proposition two. But this is not the case.

In proposition one, "light" posits a word meaning the opposite of "heavy" or massive. In proposition two, however, the same word is used to mean the opposite of "dark" (not the opposite of "heavy"). This is a kind of cheating with language, which brings us to our next important point.

Many, if not most, of the errors encountered in informal logic classes have to do with the misuse of language. Logicians consider many errors in language use also t be errors in logic. This should give the teacher -- and the student -- pause to think about the relationship between logic and language. The phrase best describing this relationship is "mutual interdependence." Each needs the other to do its job well.

I'll not elaborate on this idea at the moment, but have here mentioned it to incite thinking about just what sort of thing logic is, and why it is important for Christians to familiarize themselves with its basics.

If you find yourself a bit stressed about the hoopla of it all, take a deep breath, relax, and just take it one bite at a time. By this I mean "lighten up," which is not to be confused with the command to give off feathers.

[Today's brief exercise in logic was brought to you by the Icarus Society. Don't just think. Fly.].

Just for fun: Here are a few other statements you can analyze for logical problems. What makes them erroneous and just where does the fault lie in the reasoning? [This is the kind of stuff you should find in logic texts but won't.].

1. Always go to other people's funerals, or they won't go to yours.
2. If a man speaks in a forest with no woman around to hear him, is he still wrong?
3. There are three kinds of people: Those who can count and those who can't.
4. Down with protesting.
5. Logicians are pathological liars. Marc is a logician. Therefore, Marc is a pathological liar. And Marc was responsible for this syllogism.
6. I've had amnesia for as long as I can remember.