From PhilPapers forum Philosophy of Mind:

2010-07-02
Dretske on seeing
Reply to Mohan Matthen
Mohan, I'm not saying that. I'm saying (and I thought I was following through on your way of putting things) something about that species of determinacy (centered on object seeing) that interested Dretske that remained in the absence of beliefs or merely alongside beliefs and alongside propositions. I was trying to undermine (which is what the grounds argument gives me) any connection with the phenomenology. I may regret saying this—it's uncouth—or it's even a kind of an imposing of the Millian phenomenon, stretching the non-descriptive (and that's me suppressing the obvious links to causal theories). My point about grounds being inconclusive (in the sense of the passage I was referring to) as a support to reasoning should be familiar enough from elsewhere, but I'll give the whole passage I mentioned and perhaps you'll say whether you think it's relevant:

Smith and Jones have the same evidence (grounds) for belief that p, where the evidence consists of the proposition p v (p&q). Both subjects come to believe that p on this basis of the evidence (and no other evidence). In the case of Smith, the mechanism for generating the belief is an inference which instantiates a tendency to invalidly infer p from any sentence of the form 'p v q'. In the case of Jones, the mechanism is an inference which is based on an internalized valid inference schema (of which several are possible). It seems clear to me that only Jones has a justified belief that p, even though they have the same grounds.

(Alston quoting Swain on Alston)