1 Understanding Argument Structure

The parts of an argument

An argument is a set of connected statements offered to support a position. To understand one, identify what the author wants readers to accept, why the author thinks they should accept it, what information supports the reasoning, and what unstated ideas connect that information to the conclusion.

Claims, reasons, and support

A claim is a statement the author asks readers to accept. The main claim is the argument’s overall position; supporting claims are smaller points that help establish it. A reason explains why a claim should be accepted. Reasons are often claims themselves and may also need evidence.

Evidence is information offered to support a reason or claim, such as observations, records, data, examples, or expert findings. Evidence is not automatically convincing: its relevance and reliability matter.

An assumption is an unstated idea that must be true for a reason or piece of evidence to support a claim. In the Toulmin model, this connecting idea is called a warrant. Making assumptions explicit can reveal gaps in reasoning.

A conclusion is a claim that the argument’s reasons and evidence are meant to establish. The terms claim and conclusion overlap: a conclusion is a claim in its role as the point being supported. A statement’s role can change in a longer argument: an intermediate conclusion that has been supported may itself become a reason for the main conclusion.

Mapping the support

An argument map makes the connections among an argument’s statements visible. Rewrite the key points in your own words, then arrange them to show which statements support which others. In a complex argument, one conclusion may support a further conclusion; show each supporting point as a separate branch or step, including intermediate conclusions where needed.

Some premises work together and need one another, while others offer separate, independent support. A map helps distinguish these structures and can expose missing links. It clarifies the argument’s structure, but it does not by itself prove that the argument is sound.

A practical method

Use this sequence to analyze an argument:

1. Find the main conclusion. Ask, “What does the author most want me to believe or do?” Words such as therefore, so, and as a result can signal a conclusion, but a conclusion may appear without an indicator word.

2. List the reasons. Ask, “Why does the author think this conclusion is true?” Words such as because, since, and given that can introduce reasons, but context matters more than the wording.

3. Separate evidence from interpretation. Identify which statements report information and which explain what that information means.

4. Identify assumptions. Ask, “What must be true for this reason to support that claim?” State any important missing link as a complete sentence.

5. Trace the support. Show how evidence supports reasons, and how reasons support conclusions. Include intermediate conclusions when needed.

6. Check the links. Ask whether each reason is relevant, whether the evidence is adequate for the claim, and whether an assumption is reasonable. A clear map reveals structure but does not, on its own, establish that the argument is sound.

Example: extending library hours

Consider the proposal that the school library should stay open until 6 p.m. on weekdays. Sign-in records showed that 72 students used the library after 4 p.m. at least once during the previous month. That count is evidence; it is not, by itself, the recommendation.

The reasoning interprets the count as suggesting that students need a place to study after classes. The argument then depends on the assumption that, if students need a supervised study space after school, keeping the library open later is an appropriate way to meet that need. The main claim, which is also the conclusion, is that the library should stay open until 6 p.m. on weekdays. The school’s ability to schedule staff for the extra hours is an additional supporting point about feasibility.

To test the links, ask whether 72 students represent substantial demand, whether those students would use the library during the proposed hours, and whether staffing is feasible. These questions examine the evidence, the interpretation, and the practical support for the proposal.