2 Claims, Evidence, and Assumptions
Learn how to distinguish claims, premises, conclusions, and evidence, and how to uncover and assess the unstated assumptions that connect an argument's support to its conclusion.
Claims, premises, and conclusions
Arguments connect statements that can be evaluated as true or false. To understand an argument, identify what is asserted, what reasons are offered, and what the audience is expected to take for granted.
A is an assertion presented as true or worth accepting. Claims can play different roles: a may be a supporting reason, the point the reasons support, or a statement that is not part of an argument.
A is a offered as a reason for accepting another . The is the those reasons are intended to support. In a simple argument, premises lead to a :
The library should extend its evening hours because many students study after work, and the library is often full before it closes.
Here, the is that the library should extend its evening hours. The premises are that many students study after work and that the library is often full before it closes.
and support
Words such as because, since, and given that often introduce premises. Words such as therefore, so, and thus often signal a . These words are clues, not guarantees: determine each statement's role by how it functions in the reasoning.
is information used to support a or . It may include observations, measurements, records, examples, or testimony. can itself appear as a , but the terms describe different aspects: identifies a statement's role in the reasoning, while describes its supporting function or informational basis.
In a survey of library users, 68% said they would use the library after 8 p.m. Therefore, the library should extend its evening hours.
The survey result is presented as a , and the recommendation is the . To evaluate the support, ask whether the is accurate, relevant, and sufficient. A survey may be relevant, for instance, but its value depends partly on who was surveyed and how the survey was conducted.
Unstated assumptions
An is a an argument depends on without explicitly asserting. Arguments often leave part of their reasoning unstated, so identifying their explicit premises and may not reveal everything needed to assess the support.
In the library example, one possible is that extending the hours is a practical way to meet students' needs. Another is that enough students would use the later hours to justify the cost. These ideas connect the to the recommendation, but the explicit premises alone do not establish them.
Finding and testing assumptions
Use these steps to identify and test a possible unstated :
State the and the explicit premises.
Ask why the premises should make the more likely.
Identify the unstated idea needed to connect the premises to the .
Test the idea: would the argument weaken if it were false, and what additional information might support or challenge it?
In the library example, the survey supports the view that some users want later hours. The recommendation also depends on practical considerations such as staffing and cost. Identifying these assumptions does not automatically refute the argument; it shows what else must be considered to assess it fairly.