Either there a reality and then there a basis or there reality in the first place and it's meaningless to speak about things having a basis in reality.
I mean do you believe that reality has a basis in reality?
I think we mean different things by "basis in reality". I use it to refer to something correlating with the real world, and evidence that demonstrates such a connection either probable or certain. Probability, of course, can only work if probability were somehow demonstrated valid.
Circular arguments do not count as a basis in reality, hence your argument, which assumes the existence of physical brains, does not work.
I've raised arguments for philosophical scepticism before, which have mostly been argued against in a Popper-esque manner of arguing that even if we don't know anything with certainty, we can have legitimate knowledge on probabilities.
The problem with this, however, is how you answer a sceptic about the notion of probability having a correlation with reality. Probability depends upon axioms of probability- how are said axioms to be justified? It can't be by definition, or it has no correlation to reality.