Amusing that you dismiss philosophy in the first paragraph and then go right ahead and engage in it in the second.
Yes, as probably becomes evident from my other posts, I am just disappointed by the shallowness of most philosophy out there. In the sense that I consider mathematics to be philosophy, of course I accept it. I just don't like that almost all non-mathematical philosophy texts I have encountered start from invalid assumptions.
I think "brain in a vat" only makes a stronger case for mathematics. After all, in the end what else but information and it's transformation matters? Everything else can be stripped away. And stuck with pure information, I think we are talking maths.