When we say an argument is an attempt to convince, what exactly is it we’re
supposed to be convinced of? To do something? If we are to try to reason using
arguments, the point is that something is true. And what is that something?
A sentence, for it’s sentences that are true or false. And only certain kinds of
sentences: not threats, not commands, not questions, not prayers. An attempt
to convince, in order to be classified as an argument, should be couched in
plain language that is true or false: declarative sentences.