Definition
An argument, in the logical sense, is a set of statements in which one or more — the premises — are offered as reasons for accepting another — the conclusion. The crucial feature is the inferential relationship between the parts: an argument is not merely a list of claims but a claim that some claims support another. This distinguishes it from explanation, description, and assertion.
Logicians evaluate arguments along two independent axes. Validity concerns the structure: does the conclusion follow from the premises if they are taken as true? Soundness concerns the content: are the premises actually true? A valid argument with true premises is sound; a valid argument with false premises is unsound but still valid. The two assessments must not be conflated.
Why it matters
How it works
To analyze an argument, the first step is to reconstruct it in standard form: list each premise on a separate line, draw a horizontal line, and state the conclusion below. This forces the implicit structure into the open. Once the form is visible, two questions can be asked separately. Is the inference valid — does the conclusion follow necessarily (deductively) or with strong probability (inductively) from the premises? And are the premises themselves true?
Most real-world arguments are enthymemes, meaning that one or more premises are left unstated because they are taken as obvious or shared by the audience. The act of reconstructing an argument often reveals these hidden premises, and many disputes that seemed to be about the conclusion turn out to be about an unspoken assumption. This is why logicians spend so much effort on premise-identification: the disagreement frequently lives somewhere the original speaker never named.