# probability theory

Probability theory is the branch of mathematics that deals with the possible outcomes of events
and their relative likelihoods. While mathematicians agree on how to calculate
the probability of certain events and how to use those calculations in certain
ways, there's plenty of disagreement as to what the numbers actually mean.
Probability divides into two main concepts: **aleatory probability**,
which represents the likelihood of future events whose occurrence is governed
by some random physical phenomenon like tossing dice or spinning a wheel;
and **epistemic probability**, which represents our uncertainty
of belief about past events that either did or didn't occur, or uncertainty
about the causes of future events. The latter, for example, is what we're
talking about when we say that it's "probable" that a certain suspect committed
a crime based on the available evidence. It is an open question whether
aleatory probability is reducible to epistemic probability based on our
inability to precisely predict every force that might affect the roll of
a die, or whether such uncertainties exist in the nature of reality itself,
particularly at the level of quantum mechanics.