Claims, evidence, reasoning, introductions and conclusions

The CER framework

Whether you are writing a science lab report, a history response or an English essay, strong arguments share the same backbone: CER.

• Claim: What do you think is true?
• Evidence: What information supports it?
• Reasoning: Why does the evidence prove the claim?

Many students are good at claims and evidence but skip reasoning. Reasoning is where you show your thinking, and it is often what separates an average answer from an excellent one.

Claims

A claim is an arguable statement. It is not a fact everyone already agrees with, and it is not just a topic.

Qualities of a strong claim

• Arguable: a reasonable person could disagree.
• Specific: focused enough to support in the space you have.
• Defensible: can be backed with evidence.
• Clear: stated directly, usually in one sentence.

Evidence

Evidence is the information that supports your claim.

Types

• Quantitative: statistics, measurements, data.
• Qualitative: observations, descriptions, examples.
• Textual: quotations and paraphrases from texts.
• Expert testimony.
• Experimental results (in science).

Quality

Strong evidence is:
– Relevant: directly connected to the claim.
– Sufficient: enough to be convincing (often two or more pieces).
– Credible: from reliable sources.
– Specific: precise rather than vague.

Reasoning

Reasoning explains how and why the evidence supports the claim. It often connects the evidence to a general principle or scientific idea. That underlying principle is sometimes called the warrant.

Example (science)

• Claim: The unknown liquid is not pure water.
• Evidence: It boiled at 104°C at sea level.
• Reasoning: Pure water boils at 100°C at sea level. Because dissolved substances raise the boiling point, a boiling point of 104°C indicates something is dissolved in the liquid.

Example (literature)

• Claim: In Wonder, Jack’s betrayal is a turning point that tests Auggie’s trust.
• Evidence: On Halloween, Auggie overhears Jack telling other boys that he only spends time with Auggie because the principal asked him to.
• Reasoning: Because Jack had seemed like Auggie’s first real friend, learning that the friendship may have been an assignment devastates Auggie and makes him question whether anyone at school is genuine. The scene shifts the story’s focus from fitting in to learning whom to trust.

Reasoning sentence starters

• This shows that … because …
• Since [principle], this evidence means …
• This is significant because …
• If …, then …; therefore …

Introductions

An introduction has three jobs:

1. Engage the reader (hook).
2. Provide context (background information, definitions, title and author).
3. State the claim (thesis).

Hook strategies

• A striking statistic
• A provocative question
• A brief anecdote
• A relevant quotation
• A vivid description

Model introduction

Every summer, the downtown core of Montreal can be several degrees hotter than nearby parks. This “urban heat island” effect is caused by asphalt, concrete and a lack of shade. As heat waves grow more frequent, cities must respond. Planting trees along streets and in schoolyards is one of the most effective and affordable ways to cool neighbourhoods, improve health and reduce energy use.

Conclusions

A conclusion should leave readers with a clear sense of your argument and why it matters.

1. Restate the claim in fresh words.
2. Synthesize the main reasons, showing how they fit together.
3. Extend: explain broader significance, offer a call to action, or pose a thought-provoking question.

Model conclusion

Trees are not just decoration; they are infrastructure. By lowering temperatures, filtering air and reducing the need for air conditioning, urban forests protect residents and budgets alike. If cities invest in planting today, the next generation will inherit streets that are not only cooler but healthier.

Avoid

• Repeating the introduction word for word.
• Introducing new evidence.
• Ending with That’s why I think… or The end.
• Apologizing or weakening the claim (This is just my opinion).

Putting it all together

Paragraph structure with CER:

(Claim / topic sentence) Planting trees improves public health.
(Evidence) A 2015 study of Toronto neighbourhoods found that residents of blocks with more street trees reported better health and fewer heart-related conditions.
(Reasoning) Trees filter pollutants and lower temperatures, both of which reduce stress on the heart and lungs. Therefore, increasing tree cover can directly benefit residents’ health.

Common mistakes

• Claims that are facts or simple preferences.
• Evidence without reasoning.
• Reasoning that repeats the evidence instead of explaining it.
• Generic hooks like Have you ever wondered…? used without purpose.
• Conclusions that just repeat the thesis.

Try it yourself

1. Turn this topic into a claim: School uniforms.
2. Provide reasoning for this evidence and claim. Claim: Plants need light to grow. Evidence: The plant kept in a dark closet turned yellow and wilted, while the one by the window grew 5 cm.
3. Write a hook for an essay arguing that students should learn financial literacy.
4. Write a final “extend” sentence for a conclusion about reducing food waste.

Possible answers: 1. School uniforms reduce peer pressure and help students focus on learning. 2. Plants use light to make food through photosynthesis; without light, the closet plant could not produce enough energy, so it weakened, while the plant in sunlight grew. 3. Most Canadian teens will sign a phone contract before they ever learn what interest is. 4. If every household cut its food waste in half, we could feed millions without planting a single extra acre.

Study tip

Highlight your claim in one colour, evidence in another and reasoning in a third. If a paragraph has little of the third colour, add more explanation.

Quick recap

• A claim is arguable, specific and defensible.
• Evidence must be relevant, sufficient, credible and specific.
• Reasoning explains why evidence proves the claim.
• Introductions engage, provide context and state the claim.
• Conclusions restate, synthesize and extend.