Lesson 2 - 25% of Exam
Critical Thinking
In This Lesson
1. Argument Structure
Understanding argument structure is fundamental to legal reasoning and the PhiLSAT.
Components of an Argument
- Premise: A statement that provides evidence or reasons for the conclusion.
Signal words: because, since, given that, for, as, due to
- Conclusion: The main claim or point the argument is trying to prove.
Signal words: therefore, thus, hence, so, consequently, it follows that
- Assumption: An unstated premise that must be true for the argument to work.
Often the gap between premises and conclusion
Example Analysis
"All lawyers must pass the bar exam. Maria passed the bar exam. Therefore, Maria is a lawyer."
- Premise 1: All lawyers must pass the bar exam.
- Premise 2: Maria passed the bar exam.
- Conclusion: Maria is a lawyer.
- Flaw: Passing the bar doesn't mean you ARE a lawyer (you could be someone else who passed).
2. Types of Reasoning
Deductive Reasoning
General to Specific
- • If premises are true, conclusion MUST be true
- • Conclusion is certain (if valid)
- • All A are B. X is A. Therefore X is B.
All contracts require consideration. This agreement lacks consideration. Therefore, this is not a valid contract.
Inductive Reasoning
Specific to General
- • Premises support but don't guarantee conclusion
- • Conclusion is probable (not certain)
- • Based on patterns and observations
In the past 10 cases, juries convicted defendants with similar evidence. This defendant will likely be convicted.
3. Logical Fallacies
Fallacies are errors in reasoning that undermine arguments. Recognizing them is essential for law.
Common Fallacies
- Ad Hominem: Attack on the person, not the argument.
"His argument is wrong because he's a known liar."
- Straw Man: Misrepresenting opponent's position.
"You want lighter sentences? So you think criminals should go free?"
- False Dilemma: Only two options when more exist.
"Either we ban all guns or accept mass shootings."
- Slippery Slope: Chain of unlikely consequences.
"If we allow this, soon everything will be legal."
- Circular Reasoning: Conclusion restates premise.
"The law is just because it's the law."
- Appeal to Authority: Expert outside their field.
"This actor says the defendant is innocent."
- Hasty Generalization: Conclusion from insufficient evidence.
"Two cases failed, so all similar cases will fail."
- Red Herring: Irrelevant information to distract.
"Yes, my client stole, but think of his children."
More Fallacies
- Post Hoc: Assuming causation from sequence. "After the law passed, crime dropped. The law caused it."
- Appeal to Emotion: Using feelings instead of logic. "Think of the victims' families..."
- Bandwagon: Everyone believes it, so it must be true.
- False Cause: Incorrect causal relationship between events.
4. Strengthening & Weakening Arguments
A key PhiLSAT skill is identifying what strengthens or weakens an argument.
To Strengthen
- • Add evidence supporting the conclusion
- • Eliminate alternative explanations
- • Support the assumption
- • Show the connection between premises and conclusion
To Weaken
- • Add evidence against the conclusion
- • Provide alternative explanations
- • Attack the assumption
- • Show the premises don't support conclusion
5. Identifying Assumptions
Assumptions are unstated premises that must be true for the argument to work.
Finding Assumptions
- Identify the conclusion
- Identify the stated premises
- Find the gap between premises and conclusion
- The assumption bridges this gap
Example
"Crime rates have increased since the new policy. The policy should be reversed."
Assumption: The policy caused the increase in crime rates (not some other factor).
6. Necessary vs Sufficient Conditions
Understanding these concepts is crucial for legal reasoning.
Necessary Condition
Required but not enough by itself.
"You must pass the bar to practice law."
Passing is necessary, but passing alone isn't sufficient (you also need a license, etc.)
Sufficient Condition
Enough by itself to guarantee the result.
"If you commit murder, you've committed a crime."
Murder is sufficient for crime, but crime doesn't require murder (theft is also crime).
PhiLSAT Critical Thinking Tips
- ✓Practice identifying conclusions first - this anchors your analysis.
- ✓Learn all fallacy types - they appear frequently on the exam.
- ✓Think about assumptions - what must be true for the argument to work?
- ✓Practice with LSAT materials - similar question types.