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Example of an early argument map, from Richard Whately's Elements of Logic (1852 edition). Argumentation theory is the interdisciplinary study of how conclusions can be supported or undermined by premises through logical reasoning.
An argument map or argument diagram is a visual representation of the structure of an argument.An argument map typically includes all the key components of the argument, traditionally called the conclusion and the premises, also called contention and reasons. [1]
Being a valid argument does not necessarily mean the conclusion will be true. It is valid because if the premises are true, then the conclusion has to be true. This can be proven for any valid argument form using a truth table which shows that there is no situation in which there are all true premises and a false conclusion. [2]
Deductive arguments can be valid, and the valid ones can be sound: in a valid argument, premises necessitate the conclusion, even if one or more of the premises is false and the conclusion is false; in a sound argument, true premises necessitate a true conclusion. Inductive arguments, by contrast, can have different degrees of logical strength ...
The corresponding conditional of a valid argument is a logical truth and the negation of its corresponding conditional is a contradiction. The conclusion is a necessary consequence of its premises. An argument that is not valid is said to be "invalid". An example of a valid (and sound) argument is given by the following well-known syllogism:
An argument is valid if and only if it is the case that whenever the premises are all true, the conclusion must also be true. If there exists a logical interpretation where the premises are all true but the conclusion is false, the argument is invalid. Key to evaluating the quality of an argument is determining if it is valid and sound.
Consider the modal account in terms of the argument given as an example above: All frogs are green. Kermit is a frog. Therefore, Kermit is green. The conclusion is a logical consequence of the premises because we can not imagine a possible world where (a) all frogs are green; (b) Kermit is a frog; and (c) Kermit is not green.
The arguments advanced are (for the most part) defeasible, meaning that they are subject to defeat as new relevant evidence comes in that refutes the argument. Conclusions are accepted on a presumptive basis, meaning that in the absence of evidence sufficient to defeat it, a claim that is the conclusion of an argument can be tentatively ...