Common logical fallacies and reasoning errors - Ad hominem a...

Learning Outcomes

By the end of this article, you will be able to identify ad hominem attacks, understand their impact on argument strength, and recognize how these fallacies appear in LSAT questions. You will also gain the skills to analyze arguments for this specific flaw, distinguish it from other errors, and apply clear strategies to avoid common exam traps.

LSAT Syllabus

For LSAT, you are required to understand the nature of logical fallacies, especially how they weaken argument reasoning. This article focuses your revision on:

• Recognizing ad hominem attacks in arguments
• Evaluating how ad hominem affects argument validity
• Answering LSAT flaw and reasoning questions involving ad hominem
• Distinguishing ad hominem from other common flaws (like straw man or appeals to authority)

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which statement best illustrates an ad hominem attack in an argument?
   1. Evaluating the factual accuracy of evidence
   2. Attacking the character of the argument’s author
   3. Showing the argument uses a hasty generalization
   4. Providing alternative data
2. On LSAT flaw questions, when should an ad hominem be identified as the primary error?
   1. Any time the argument disagrees with another person
   2. Only when personal traits irrelevant to the argument's merits are cited as a reason for rejection
   3. When the author provides no evidence at all
   4. Whenever sources are questioned

3. True or false? If an argument attacks an opponent’s financial interest without addressing the reasoning, it likely contains an ad hominem fallacy.

Introduction

Ad hominem attacks are a frequent reasoning error tested on the LSAT. They appear in flaw, reasoning, and even some strengthen/weaken questions. Understanding this fallacy is essential, as examiners expect you to spot and explain it whenever an argument attacks a person rather than the substance of their reasoning.

Key Term: ad hominem
An ad hominem fallacy is an error that dismisses an argument based on an attack on the person making it, instead of addressing the merits of the reasoning or evidence.

Why Ad Hominem is a Flaw

On the LSAT, every argument should be judged by its logic and evidence. An ad hominem replaces critical evaluation with a personal attack, which is always irrelevant to whether the reasoning is valid.

Arguments containing ad hominem attacks almost never provide substantive counter-argument. Instead, they try to undermine trust based on motivations, background, reputation, or other personal factors unrelated to the actual conclusion.

Key Term: logical fallacy
A reasoning error that renders an argument invalid, often by violating fundamental principles of logical analysis.

Types of Ad Hominem Attacks

The LSAT commonly tests two forms of ad hominem:

• Attacks on the person’s character, honesty, or background
• Attacks based on alleged motives or interests (e.g., “You can’t trust him about tax policy; he works for a bank.”)

Key Term: personal attack
Criticizing the individual making the argument rather than analyzing the actual reasoning or evidence.

Why Ad Hominem is Tested

The LSAT assesses your ability to separate reasoning from irrelevant information. Ad hominem fallacies are included to ensure you can:

1. Recognize irrelevant attacks in an argument
2. Trace arguments back to conclusion and premise structure
3. Articulate why the attack does not address the truth of the conclusion

Worked Example 1.1

Argument:
"Ms. Torres claims the city’s budget is mismanaged. But Ms. Torres was recently fined for a parking violation, so we shouldn’t trust her assessment."

What is the flaw?

Answer:
The argument attacks Ms. Torres's character (parking violation) instead of contesting her reasoning about the city budget. This is an ad hominem error.

Worked Example 1.2

Argument:
"A report criticizing water quality should be ignored because the authors stand to benefit financially if the city buys new filters."

Is this an ad hominem?

Answer:
Yes. The argument focuses on the potential financial motive of the authors rather than addressing whether the report’s analysis is correct.

How Ad Hominem Appears on the LSAT

Ad hominem is most frequently tested in flaw questions. The question stem may ask:

• "Which one of the following is a flaw in the reasoning?"
• "The argument proceeds by attacking the person instead of addressing the substance of the claim."

Sometimes, ad hominem is disguised. The argument may refer to bias, conflict of interest, or motivations—be alert for any reasoning that shifts the focus from ideas to people.

Exam Warning

On the LSAT, not all references to a person’s character are ad hominem. Only identify the flaw if the argument equates personal characteristics with argument invalidity, without further evidence.

How to Identify and Avoid the Trap

1. Ask: Does the argument rebut reasoning, or merely attack the arguer?
2. Look for phrases indicating personal criticism: “cannot be trusted,” “biased,” “self-interested,” etc.
3. Ask if these traits are the actual reason the conclusion is said to be false.
4. Remember: Attacking a witness’s truthfulness is only relevant if their personal veracity is the sole premise for a factual claim.

Revision Tip

Don’t confuse ad hominem with other flaws such as straw man (misrepresenting the opponent’s view) or appeal to authority (relying on expert opinion about an irrelevant field).

Worked Example 1.3

LSAT-style stem:
"The argument is flawed because it:
a) Assumes that all claims from biased individuals are false
b) Presents irrelevant personal criticism as a reason to reject a claim
c) Relies on an appeal to popularity
d) Presumes a causal relationship without evidence"

Answer:
b) Presents irrelevant personal criticism as a reason to reject a claim. This is the definition of an ad hominem flaw.

Worked Example 1.4

Argument:
"Senator Everett’s argument for clean energy subsidies is worthless because she owns stock in a solar panel company."

Why is this a flaw?

Answer:
Owning stock may show a potential bias, but it does not invalidate the senator’s reasoning. The argument must address the merits, not investment holdings.

Summary

Ad hominem attacks are a classic logical flaw on the LSAT. Always distinguish between attacks on reasoning (valid) and attacks on the person (invalid). Spotting this fallacy will help you eliminate distractors and select the correct answer in flaw, reasoning, and some weaken question types.

Key Point Checklist

This article has covered the following key knowledge points:

• Ad hominem attacks undermine argument validity by targeting people, not reasoning
• The LSAT tests ad hominem in flaw, reasoning, and some weaken questions
• Focus on personal criticism that replaces genuine analysis of evidence or logic
• Not all references to bias or motive are ad hominem—context matters
• Use a step-by-step check to identify this flaw in exam questions

Key Terms and Concepts

• ad hominem
• logical fallacy
• personal attack