In [[logic]], the '''argument form''' or ''test form'' of an [[Argument (Logic)| argument]] results from replacing the different words, or sentences, that make up the argument with letters, along the lines of [[algebra]]; the letters represent logical ''[[variable]]s''. The ''sentence forms'' which classify argument forms of common important arguments are studied in [[logic]].

----

Here is an example of an argument:

'''A''' All humans are mortal. Socrates is human. ''Therefore'', Socrates is mortal.

We can rewrite argument A by putting each sentence on its own line:

'''B'''
:All humans are mortal.
:Socrates is human.
:''Therefore'', Socrates is mortal.

To demonstrate the important notion of the ''form'' of an argument, substitute letters for similar items throughout '''B''':

'''C'''
:All S are P.
:''a'' is S.
:''Therefore'', ''a'' is P.

All we have done in '''C''' is to put 'S' for 'human' and 'humans', 'P' for 'mortal', and '''a''' for 'Socrates'; what results, '''C''', is the ''form'' of the original argument in '''A'''. So argument form '''C''' is the form of argument '''A'''. Moreover, each individual sentence of '''C''' is the ''sentence'' ''form'' of its respective sentence in '''A'''.<ref>Hurley, "1.5 Argument forms; proving invalidity"</ref>

Attention is given to argument and sentence form, because ''form is what makes an argument [[validity|valid]] or [[cogency|cogent]]''. Some examples of valid argument forms are [[modus ponens]], [[modus tollens]], and the [[disjunctive syllogism]]. Two invalid argument forms are [[affirming the consequent]] and [[denying the antecedent]].

== References ==
Hurley, Patrick J. (1988). ''A concise introduction to logic''. Belmont, Calif. : Wadsworth Pub. Co. ISBN 0534089283

== Notes ==
<references/>

==See also==
*[[Analytic proposition]]
*[[Synthetic proposition]]
*[[logical form]]

[[Category:Arguments]]
{{logic-stub}}