← L² Lab
🧠 Critical Thinking
Card 21
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Can you prove something is true by assuming it's true?

💭 How to Think About This

"Why should I trust you?" "Because I'm trustworthy!" "How do I know you're trustworthy?" "Because I said you should trust me!" This is circular reasoning - using your conclusion as your premise. It's like a dog chasing its own tail!

🔒 Start writing to unlock hints

CIRCULAR REASONING (also called "begging the question") = when your CONCLUSION is hidden in your PREMISE. You assume what you're trying to prove! Example: "The Bible is true because it says so in the Bible." The argument goes in a circle - no external support!

Why it feels convincing: The logic is TECHNICALLY valid (if premise is true, conclusion follows). But it proves NOTHING because you never established the premise! It's like saying: A because B, and B because A. Where's the actual EVIDENCE?

• "I'm qualified for the job because I'm the best candidate." (Restating claim!)

• "Murder is wrong because killing people is immoral." (Same statement!)

• "She's lying because she's a liar." (Assumes conclusion!)

• "This law is just because it's the right thing to do." (Circular!)

Ask: "Is the premise just restating the conclusion in different words?" or "What independent evidence supports the premise?" If the only support for A is B, and the only support for B is A - you're in a circle! Demand external evidence!

Circular reasoning uses the conclusion as support for itself - proving nothing!

The structure:

• Claim: A is true

• Evidence: A is true (just restated differently)

• Conclusion: Therefore, A is true

You've gone in a circle!

Why it's fallacious:

An argument needs INDEPENDENT premises to support the conclusion. Circular reasoning has no independent support - it just assumes what it's trying to prove!

Subtle examples:

• "Opium puts people to sleep because it has dormitive virtue" (dormitive = sleep-causing - just restated!)

• "We know God exists because the Bible says so, and the Bible is God's word, so it must be true"

• "Democracy is the best system because majority rule is the right way to govern"

Detection technique:

1. Identify the conclusion

2. Identify the premises

3. Check: Are premises just conclusion in disguise?

4. Ask: What EXTERNAL evidence supports premises?

Not the same as: Valid reasoning that uses established facts. "All mammals breathe air. Whales are mammals. Therefore whales breathe air." ✓ Not circular - "all mammals breathe air" is independently verifiable!

🤔 Which thinking lens(es) did you use?

Select all the lenses you used: