In response to ej’s new comments on the very first blog post here and subsequent emails, I’ll post the following to give him and perhaps others a chance to respond to one of the main issues of disagreement between us:
Frankfurt’s demon is on the loose again. His ordinary activity is in making sure people beat their wives and other assorted horrendous actions. He’s now much more civilized. He limits his activity to restricting what propositions are considered, and he’s picking on you. For some propositions, he just won’t let you consider them. As usual, however, this doesn’t require anything on his part: he just monitors your thought life and leaves you alone, unless he detects you initiating the activity of considering one of the propositions in question.
The demon has a name: he’s the Shope demon. He picks which propositions to prevent you from considering solely to undermine certain internalist assumptions about justification. In particular, Shope’s demon picks (some) propositions that are justified for you by your total body of evidence.
So what internalist assumptions are affected? First, notice that the description of the demon rules out theories that insist that only propositions you’ve considered or entertained can be justified for you. Such theories aren’t very plausible anyway. So consider more plausible theories that involve the following idea: a justification for believing p involves something that you would, or could, or might cite in defense of p.
There are lots of known problems here, many of which affect all but the weakest modal claim that your evidence is something you could cite (if you’re from where I’m from and love double modals, you might say “something you might could cite”) in defense of p. Shope’s demon flashes a grin and emits a mephistophelian laugh. Internalists can’t have the claim that you’ve only got justification for propositions you can consider; Frankfurt sold it to Shope’s demon.
Shope’s demon has allies, too. I don’t know exactly the character of their activity, but I can describe it indirectly: qualify the above account to evade Shope’s demon, and you’ll discover the precise character of the activity of one of his allies.