How we change what others think, feel, believe and do
In speaking in support of, or against, a subject, making propositions gains agreement and commitment, changing the minds of your audience.
A proposition is a viewpoint that you will create, defend or destroy. It should be worded as a declarative sentence that unambiguously expresses your position.
A proposition can be the main point of your position. It can also be a single supportive element. It can also be an opposing proposition that you will disprove.
A proposition should first be debatable in that arguments may be marshaled for and against the proposition. This is important for the persuader, too, as one way of persuading is putting up arguments against the proposition and knocking them down. Paraphrasing Sherlock Holmes, 'When all other propositions have been disproven, the truth, however improbable, will be proven.'
As well as arguing for and against the case, it should be possible to conclusively prove the truth of your proposition. Karl Popper also added the importance of falsifiability. If you cannot possibly prove something to be false, then you neither can prove it to be true.
There are three types of proposition: fact, value and policy.
Proposition of Fact
A proposition of fact is a statement in which you focus largely on belief of the audience in its truth or falsehood. Your arguments are thus aimed at getting your audience to accept the statement as being true or false.
Proposition of Value
In a proposition of values, you make a statement where you are asking your audience to make an evaluative judgment as to whether the statement is morally good or bad, right or wrong. This may be done by comparing two items and asking them which is better.
Propositions of Policy
A proportion of policy advocates a course of action. In this, you ask your audience to endorse a policy or to commit themselves to a particular action.