Exposing PseudoAstronomy

November 27, 2009

Logical Fallacies: Circular Reasoning, AKA the Tautology


In my continuing series on logical fallacies, today we’re going to explore circular reasoning, more formally known as a “tautology” or a “tautological argument.”

What is a Tautology?

Throughout this post, I’m probably going to mainly use the term “tautology” rather than “circular reasoning” because it’s less to type. Circular reasoning is, like most fallacies, just what it sounds like: Making a circular argument, or when each stage of an argument refers back to the previous stage, or uses the previous stage as justification for that one. You just go around in circles.

Another way in which a tautological argument is used is to simply state the same thing twice, but in different ways. Like saying, “This is a brand-new never-before seen product!” is considered a tautology because “brand-new” and “never-before seen” mean the same thing.

The Example of Biblical Authority

This isn’t directly related to astronomy, but it underlies almost all young-Earth creationist claims and so I’ll put it in here. It would seem that the idea of biblical authority would be better-relegated to my upcoming post on the Argument from Authority, but it actually is a tautological argument as well.

If you ask a young-Earth creationist (YEC), or probably any person who believes in the inerrancy of the Bible, why the Bible is true, you will get a tautology as illustrated in the diagram below:

Let’s have a hypothetical conversation:

Me: Why is the Bible true?
YEC: Because the Bible is infallible.
Me: Why is it infallible?
YEC: Because the Bible is the word of God.
Me: How do you know it’s the word of God?
YEC: Because the bible says it is the word of God.
Me: But how do you know that it’s telling you the truth?
YEC: Because the Bible is infallible.

We have entered the tautology. The YEC has not brought in outside information into the argument to back up the claim, they simply continue to go in circles.

Example from Family Life

An example of a tautology that’s closer to the second use I explained above is often found in every-day parlance, especially between parents and their children:

Parent: “It’s bed time, go to bed.”
Child: “Why?”
Parent: “Because I said so.”

Final Thoughts

Circular arguments and/or tautologies are yet another illogical way to argue because they do not bring any new information into the discussion. Rather, they argue what has already been (correctly or incorrectly) stated, and do not back it up with something else.


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