A posteriori stinks

Click on the title of the article to see a funny argument. A posteriori stinks because you can't make (a posteriori) claims without making assumptions, so therefore you can't prove anything using those claims. Thus, there is no such thing as a posteriori knowledge. Thus, a priori is the closest one can come to proof. If a priori claims can't prove something, nothing can. Perhaps there is some a priori verity from which the whole of existence is derived.