Abstract
In situations where we ignore everything but the space of possibilities, we ought to
suspend judgment—that is, remain agnostic—about which of these possibilities is the
case. This means that we cannot sum our degrees of belief in different possibilities,
something that has been formalized as an axiom of non-additivity. Consistent with this
way of representing our ignorance, I defend a doxastic norm that recommends that we
should nevertheless follow a certain additivity of possibilities: even if we cannot sum
degrees of belief in different possibilities, we should be more confident in larger groups
of possibilities. It is thus shown that, in the type of situation considered (in so-called
‘classical ignorance’, i.e. “behind a thin veil of ignorance”), it is epistemically rational
for advocates of suspending judgment to endorse this comparative confidence; while on
the other hand it is shown that, even in classical ignorance, no stronger belief—such as
a precise uniform probability distribution—is warranted.