I thought bore some relevance since Philip seems to be defending some interesting version of Empiricism. We must remember, however, that it is empiricism and not something else. What follows is long and sometimes convoluted and often unclear, but I think you'll see why it might be important.
Any person is justified in believing a proposition on the basis of their own perceptual state.
There have been several traditional attacks on the empiricist's position. Certainly, the argument will run, it will not be a deduction since R is not supposed to be a proposition, but rather a perceptual state of the believer. CT1 People have beliefs which are caused by states of affairs. CT2 People are, prima facie, justified in holding those beliefs which are caused in them. The problems with this position are many, two of the problems are deadly.