Probability theory is a theory, but probability is something else.
I'd prefer not to be the one to make the change, though. It is formally a branch of measure theory, and its foundations are as solid as any other branch of mathematics. Applied probability isn't just Statistics , but must be founded a priori on some particular notion of reality. There are philosophical concepts of probability which do not match or fit the mathematical theory of probability. My usage is perhaps too informal, but is conditioned by the topic residing in the Mathematics hierarchy as distinct from Philosophy .