How does formal logic focus on an argument’s structure rather than its subject matter?

Formal logic focuses on the structure of an argument rather than its subject matter by abstracting away specific content to reveal the underlying logical form.12

Logicians achieve this by replacing non-logical terms with variables, which act as placeholders for expressions of a certain type. By keeping only the logical constants—such as "and," "not," "if-then," and quantifiers—intact, the resulting formula represents the argument's structure.23

This approach allows for the evaluation of validity based solely on that structure. An inference is considered deductively valid if its form ensures that it would be inconsistent to assert the premises while denying the conclusion, regardless of whether the specific subject matter is true or false. Consequently, formal logic is concerned with discriminating between valid and invalid inference forms rather than verifying the factual accuracy of particular instances. This method enables logicians to apply tests of validity unambiguously, often using symbolic notation to manipulate these structures independently of any specific interpretation.21