For the purposes of this post, I'm assuming something like the intuitive notion of justification makes sense.
Sometimes people say:
1. "You should believe what's true, and avoid believing what's false."
Other times they say:
2. "You should believe what's justified, and avoid believing what's unjustified."
But prima facie, these are incompatible demands, since there are many true propositions which I am not justified in believing, like statements of the form "Tommorrow's winning lottery number will be ....", and 1 seems to entail that I should believe these claims, while 2 seems to entails that I shouldn't.
Puzzle: Can these two claims be made compatible? What is the relationship between these them?
first pass- Maybe we want to widescope? e.g.
1 ='Should[(Ax) Believe(x) <--> Expresses-a-Truth(x)]
2 ='Should[(Ax) Believe(x) <--> You-are-justified-in-believing(x)]
Though this suggests the conclusion that you should bring it about (by some kind of superhuman feat of evidence gathering?) that you are justified in believing every truth. Which is, maybe, odd.