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Think For Yourself

Claims, Evidence, and Reasoning: The Three Parts

Ages 10–14 25 min read Intermediate

Every argument has three ingredients: a claim (what you're arguing), evidence (proof), and reasoning (why the evidence supports the claim). Miss any one of these, and your argument falls apart.

The CER Framework

Claim

A clear statement of what you believe to be true. Good claims are specific and falsifiable — meaning someone could potentially prove them wrong.

  • Weak claim: "Sugar is bad." (Vague — bad how? For whom? In what amounts?)
  • Strong claim: "Consuming more than 50g of added sugar per day increases the risk of type 2 diabetes in adults." (Specific, measurable, testable.)

Evidence

Data, facts, observations, or expert testimony that supports the claim. Good evidence is:

  • Relevant — actually connected to the claim
  • Reliable — from a trustworthy source
  • Sufficient — enough to support the claim (one example isn't enough for a universal claim)

Reasoning

The explanation of WHY the evidence supports the claim. This is the bridge that most people leave out.

Bad: "Sugar is bad. A study found people who eat lots of sugar get diabetes." (Where's the reasoning?)

Good: "Consuming more than 50g of added sugar per day increases diabetes risk. A 2015 meta-analysis of 38 studies (Imamura et al., BMJ) found that each daily serving of sugary drinks increased diabetes risk by 13%. This is because excess sugar causes insulin resistance over time, which is the primary mechanism of type 2 diabetes."

The Hierarchy of Evidence

Not all evidence is equal:

  1. Strongest: Systematic reviews and meta-analyses (combining many studies)
  2. Randomised controlled trials
  3. Observational studies
  4. Expert opinion
  5. Case studies and anecdotes
  6. Weakest: "My friend said..." / "I read somewhere..."

When someone supports a claim with "I know someone who..." they're at the bottom of the evidence pyramid. When they cite a meta-analysis, they're at the top.

Tonight's Question

"Pick any claim someone made today — at school, on TV, online. What evidence did they give? Was there reasoning connecting the evidence to the claim?"

CER Practice

  1. Each person picks a claim they want to argue (e.g., "School holidays should be longer").
  2. Find real evidence to support it (spend 10 minutes researching).
  3. Write out the full CER: Claim + Evidence + Reasoning.
  4. Present to the family. Others evaluate: is the evidence reliable? Is the reasoning solid?
  5. Rate each argument 1-10. Discuss what made the strong ones strong.

Go Further

  • Research: What is a "meta-analysis" and why is it considered the strongest form of evidence?
  • Practice: Read a news article and identify the CER structure. Is anything missing?
  • Book: How to Read a Paper by Trisha Greenhalgh (2019) — understanding medical evidence.
  • Question: When experts disagree, how do you decide who to believe? (Hint: follow the evidence, not the person.)

What We Simplified

  • The evidence hierarchy isn't absolute. A well-designed observational study can be more valuable than a poorly designed randomised trial.
  • Real arguments are iterative. You don't build one perfect argument — you refine your claims as new evidence emerges.
  • CER works best in science. In ethics, philosophy, and politics, evidence looks different (moral arguments, precedents, values).

Sources

  • Imamura, F. et al. (2015). "Consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice and incidence of type 2 diabetes." BMJ, 351, h3576.
  • Greenhalgh, T. (2019). How to Read a Paper. 6th ed. Wiley-Blackwell.
  • Sackett, D.L. et al. (1996). "Evidence based medicine: what it is and what it isn't." BMJ, 312, 71-72.

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