Circular reasoning comes up every so often on the LSAT, mostly in the answer choices for flaw questions. An argument with circular reasoning uses the conclusion of the argument to support the reasoning of the argument, which is then used to support the conclusion of the argument. In other words, the argument uses the conclusion to prove itself. And that’s just not good reasoning.
Simple Examples of Circular Reasoning
Look at the following example:
Everything in this book is true. This is supported by the fact that the book itself claims that everything in it is true. Thus, the book's claim about itself must also be true because everything in the book is true.
In the above example, the conclusion is “Everything in this book is true.” Let’s call that Assertion 1. The support for Assertion 1 is “The book itself claims that everything in it is true.” Let’s call that Assertion 2. Assertion 2 is a reason to believe Assertion 1. Great. No problems so far. But the argument continues! Assertion 2 is supported by the claim “everything in the book in true.” Wait a second. That’s just Assertion 1 again. So Assertion 1 is supported by Assertion 2 which is supported by Assertion 1? That doesn’t make any sense.
This is just plain awful reasoning. You can literally justify anything using circular reasoning, and that makes it a logical fallacy. Let’s look at couple more examples.
Randy: Jim was fired for incompetence and not because of some grudge against him. That has to be the case because Jim was obviously a terrible employee. Sue: How do you know he was such a bad employee? Randy: Because he was fired!
Few people will vote for Smith for governor because Smith is not a good candidate. After all, his terrible candidacy is obvious to anyone who considers the small number of votes he will receive.
These arguments are so bad that you might consider them laughable. But they are also good illustrations of circular logic. Try to spot the moment in each argument where the conclusion is restated in order to justify the reasoning used to support the argument’s conclusion.
Trickier Example of Circular Reasoning
In the example below the reasoning is circular but harder to spot. The conclusion is not restated; rather, the conclusion is assumed by the argument’s premises.
Mindy does not want to go to any kind of graduate school other than law school. So she obviously must be going to law school. Therefore, your assertion that Sammy does not want to go to any kind of graduate school at all is wrong.
Here the conclusion is “Your assertion that Sammy does not want to go to any kind of graduate school at all is wrong.” But notice how the argument’s reasoning makes no sense unless we have already assumed that Sammy is going to grad school. This makes the reasoning circular; the argument assumes the very thing it seeks to establish.