Proofs that P:

Putnam:

Some philosophers have argued that not-p, on the grounds that q. It would be an interesting exercise to count all the fallacies in this "argument". (It's really awful, isn't it?) Therefore p.

Rawls:

It would be nice to have a deductive argument that p from self- evident premises. Unfortunately I am unable to provide one. So I will have to rest content with the following intuitive considerations in its support: p.

Unger:

Suppose it were the case that not-p. It would follow from this that someone knows that q. But on my view, no one knows anything whatsoever. Therefore p. (Unger believes that the louder you say this argument, the more persuasive it becomes).