  I discuss the meaning of probability in the Everett-Wheeler interpretation of
quantum mechanics, together with the problem of defining histories. To resolve
these, I propose an understanding of probability arising from a form of
temporal logic: the probability of a future-tense proposition is identified
with its truth value in a many-valued and context-dependent logic. In short,
probability is degree of truth. These ideas appear to be new (though I expect
correction on this), but they are natural and intuitive, and relate to
traditional naive ideas of time and chance. Indeed, I argue that Everettian
quantum mechanics is the only form of scientific theory that truly incorporates
the perception that the future is open.
