Flaws in Logical Reasoning Part I: Source Arguments

How to Identify a Source Argument

You’re likely familiar with this because it’s an often-favored style of rebuttal, particularly with children and, sadly, politicians. I’ll leave you to consider the extent of similarity between those two groups. Consider this example:

“Mayor Jones’ anti-DUI campaign should not be taken seriously. After all, the mayor himself was cited for driving under the influence in college.”

Should the mayor’s campaign be ignored based on the statement that he committed the very crime he is seeking to prevent? Of course not. An attack on the person leaves the merits of the campaign left unchallenged. Therefore, this argument against the mayor is a poor (flawed) one.

Source arguments can be easy to spot on the LSAT, as they almost always take one of two identifiable forms:

1. Focusing on the actions of the source (as in the example above).
2. Focusing on the motives of the source.

Consider this scenario. You encounter a stimulus where the author is attempting to disprove someone’s position by attacking the person or group behind that position. Next, they will ask you to describe the author’s error. What can you expect of the correct answer choice? Well, it will contain a few predictable points:

1. It will note that the author is attempting to discredit or criticize a position or claim.
2. It will state that the author is in error for focusing on the proponent or source of that claim.

Here are some examples of source arguments as described by the test makers:

• “It is directed against the proponent of a claim rather than against the claim itself.”
• “It draws conclusions about the merit of a position and about the content of that position from evidence about the position’s source.”
• “Assuming that a claim is false on the grounds that the person defending it is of questionable character.”

Stay Sharp

You should always be on the lookout for arguments that address the nature of a claim’s source instead of the contents of the claim itself. You should be able to quickly choose the answer when asked to describe that flaw with the characteristics given above. Stay tuned for Parts 2–10 in the series! Make an effort to commit the flaws we discuss to memory and you’ll find yourself well prepared to respond to nearly any argument you come across.