Belief polarization occurs when subjects who disagree on a matter of fact are exposed to a mixed body of evidence that bears on that dispute. Despite assumptions to the contrary, mutual exposure to common evidence leads to disagreements becoming more pronounced, as each person increases confidence in his or her antecedent belief. Writing in the journal Synthese, epistemologist Emily McWilliams argues that the resulting beliefs are not justified based on plausible versions of evidentialism, a popular theory of justification.