Definition:Invalid Argument

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An invalid argument is a argument in which the premises do not provide conclusive reasons for the conclusion.

Also known as

An invalid argument is also known as a fallacy.

Some authors use the term unsound argument to mean invalid argument.

However, because of the confusion about the meaning of sound argument, which can be used to mean either valid argument or proof, it is recommended that this term not be used.

Also see


In natural language, it is commonplace to discuss the nature of statements as being valid or invalid, when what is really meant is that a statement is either true or false.

Linguistic Note

The word invalid, as used in the logical context, has the stress on the second syllable: in-val' -id.

Pronounced in' -val-id, with the stress on the first syllable, the word means a person who is being treated for an illness.

So let's be careful out there.