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English Composition and Rhetoric Unit 2: Claims and evidence

A strong argument makes a clear, debatable claim and supports it with relevant evidence and commentary that explains how the evidence proves the point.

Covers: Thesis statements, claims, types of evidence, commentary, reliability

Study guide

A thesis is the central claim of an essay: a specific, arguable position the rest of the paper defends. An arguable claim is one reasonable people could disagree with, so "The sun is hot" is a fact, not a thesis. A strong thesis is specific, takes a clear stance, and often previews the reasoning: "Schools should start later because adolescent sleep patterns, academic performance and safety all improve." Your thesis can be refined as you draft.

Each body paragraph supports the thesis with its own claim, usually stated in a topic sentence. Claims need evidence. Types of evidence include facts and statistics, expert testimony, examples, research findings, anecdotes (personal stories, which are vivid but limited) and textual evidence quoted or paraphrased from sources. Choose evidence that is relevant, sufficient and appropriate for your audience.

Evidence alone doesn't make an argument; commentary does. Commentary explains how the evidence supports the claim, why it matters, and how it connects to the thesis. A common paragraph pattern is claim → evidence → commentary, often with more commentary than quotation.

Evaluate source reliability before using evidence. Credible sources have qualified authors, cite their own evidence, are current enough for the topic, come from reputable publishers, and show limited bias. Be cautious with anonymous websites, opinion presented as fact, and outdated or unsupported claims. Tests like CRAAP (currency, relevance, authority, accuracy, purpose) help structure the evaluation.

When a prompt asks "to what extent" a claim is valid, a strong thesis takes a qualified position. It says when, for whom or under what conditions the claim holds and where it breaks down. Listing pros and cons without choosing a position doesn't count as a thesis. When no sources are given, support claims with specific, concrete examples from history, current events, science, literature or close personal observation. One well-explained specific example is stronger than several broad generalizations ("people today are always on their phones").

Acknowledging other views strengthens an argument only when you name a specific opposing claim and respond to it. Vague hedges such as "some may say" or "everyone has their own opinion" weaken the position instead.

Key ideas

• A thesis states a debatable position and often previews the reasoning.
• Claims need evidence: data, examples, expert testimony, anecdotes.
• Commentary explains how the evidence supports the claim. It's the most important part.
• Evaluate sources for credibility, currency and bias.
• Facts aren't claims; a claim can be argued against.

Formulas and rules

Common mistakes

• Writing a thesis that's just a fact (no one could disagree).
• Dropping in quotes without explaining them.

Words to know

Thesis

A debatable, specific position the essay defends.

Commentary

Explanation of how evidence supports the claim.

Anecdotal evidence

A personal story used as support.

Arguable claim

A statement reasonable people could dispute; a thesis must be one.

Credible source

Expert author, recent, evidence-based, low bias.

Paragraph structure

Claim → evidence → commentary.

Claim

A statement the writer argues for.

Topic sentence

States a paragraph's main claim.

Evidence

Facts, statistics, examples, testimony or quotations that support a claim.

Expert testimony

Evidence from a qualified authority.

Statistical evidence

Numerical data supporting a claim.

Bias

A one-sided perspective that can distort evidence.

Line of reasoning

The logical sequence of claims leading to the thesis.

Sample practice questions

5 more questions like these, from level 1 to 5, are in the practice set.