Epistemologists tend to look for standards governing either full-fledged "beliefs" (including knowledge, and beliefs about probabilities) or degreed "credences" (whether precise or rough). This course focuses on standards governing a neglected third kind of state, that we might call "guesses", akin to scientific "null hypotheses" or practical "working assumptions". We will consider the philosophical importance of best guesses: e.g., arguably without initially justified (as opposed, e.g., to wild) guesses we can justify little else in philosophy—neither ethical nor even epistemological standards, nor views about the external or even internal world, nor probability assignments (and credences) nor meaning assignments nor even logic. We will consider the psychological relations among guesses, beliefs, and credences. We will consider ways to justify "educated" guesses both in the presence of (what we might guess is) evidence, and "blind" guesses in the absence of evidence. And bracketing as much as possible that we have not yet been able to justify from scratch, we will try to reconstruct what best-but-blind guesses would be about evidence, logic, meanings, probabilities, minds, environments, and ethics.