Mike
Afraid not. If you start with a proposition and use it to "prove" itself untrue: if the proposition on which you built your proof is untrue then the proof is invalid as it is based on a false premise, which means the proposition is not proved untrue after all, which means you can start with the proposition and....... (stop when bored)
Regards
JR
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1