OQ Arguments, and Crispin Wright's 'dilemma'

For any potential source of knowledge (the reliability of our senses, religious inspiration, scientific method), we cannot both (a) have it as an empirical fundamental and (b) show it to be reliable.  These two are mutually exclusive, because any demonstration that our knowledge of (b) is reliable has to be based on some other fundamental.

We also cannot say 'this must be accepted without demonstration' because we have to explain the 'must'.