more evidence can reduce confidence. The basic idea is simple. We expect that in most processes there will normally be some noise so absence of noise suggests a kind of systemic failure. The police are familiar with one type of example. When the eyewitnesses to a crime all report exactly the same story that reduces confidence that the story is true. Eyewitness stories that match too closely suggests not truth but a kind a systemic failure, namely the witnesses have collaborated on telling a lie.