How does logical validity depend on the structure of an argument rather than its subject matter?

In logic, the validity of a deductive argument is determined entirely by its form or structure, rather than the specific subject matter of its premises or conclusion. An argument is considered valid if it is impossible for its premises to be true while its conclusion is false; this guarantee of truth is a result of the argument's internal construction, not the factual accuracy of the statements themselves.123

To analyze this structure, logicians replace non-logical terms with variables, creating an inference form. For example, the arguments "Every dog is a mammal; some quadrupeds are dogs; therefore, some quadrupeds are mammals" and "Every anarchist is a believer in free love; some members of the government party are anarchists; therefore, some members of the government party are believers in free love" share the same valid structure: "Every X is a Y; some Zs are Xs; therefore, some Zs are Ys". Because this form ensures that any uniform substitution of terms resulting in true premises will automatically yield a true conclusion, the validity remains constant regardless of the content.12