A perfectly valid argument can still prove that bats are birds
Bats fly, and every flying creature is a bird, so bats are birds. The conclusion is false, yet logicians call the argument valid, because if both premises were true the conclusion could not fail. Validity concerns the shape of reasoning, not its truth, and confusing the two trips up careful thinkers constantly.
An argument is a set of premises aimed at one conclusion, offered to justify, explain or persuade. The word traces to the Latin arguere, to make bright or make known, from an ancient root meaning to shine. Scholars study argument from three angles. Logicians examine its formal structure, often in symbols. Dialecticians treat it as a way two parties work through a disagreement. Rhetoricians add an audience and insist that time and place shape how an argument lands.
Deductive arguments promise certainty: accept the premises and denying the conclusion becomes self-contradictory. Validity means no possible world makes the premises true and the conclusion false. Soundness is the stronger badge, requiring valid form plus true premises. Because validity lives in the form, an invalid pattern can be exposed by swapping in new content. 'Some men are hawkers, some hawkers are rich, so some men are rich' looks plausible until the same shape yields the conclusion that some people are zebras.
Inductive arguments trade certainty for probability. Predictions are always inductive, since the future is open, and such arguments are rated strong or weak rather than valid or invalid. A strong argument with true premises earns the label cogent, the inductive counterpart of soundness. The gap between even the best inductive support and deductive proof is what philosophers call the problem of induction. Oddly, mathematical induction, despite its name, is not inductive reasoning at all.
Modern argumentation theory stresses that everyday reasoning is defeasible: new information can cancel a conclusion that once seemed secure. Told that Tweety is a bird, you reasonably infer Tweety flies, until you learn Tweety is a penguin. Such arguments lean on generalisations true in most cases, so assessing them requires rules about what counts as a reasonable inference from a situation, not only rules of formal logic.
Source: Argument
