 Klein and Warfield (1994) argue that coherence often decreases probability. Why? Increases in coherence often come from new beliefs that make sense of our existing beliefs. A detective investigating a crime may be puzzled by conflicting testimony until she learns that the suspect has an identical twin, which explains why some witnesses report seeing the suspect in another city the day of the crime. And yet, adding the fact about the identical twin to her body of beliefs actually decreases its probability. This follows from a theorem of the probability axioms we noted earlier  (§1.2),  Conjunction Costs Probability, which says that conjoining \(A\) with \(B\) generally yields a lower probability than for \(A\) alone (unless \(p(A \wedge \neg B)=0\)). Intuitively, the more things you believe the more risks you take with the truth. But making sense of things often requires believing more.