 What makes the problem so difficult is that there are a variety of ways the causal chain of events can go wrong and thereby fail to establish a basing relation. For example, glitches in the brain, wandering thoughts, wishful thinking, strong emotions, etc., may all be implicated in deviant causal chains. It is quite difficult to clearly explain what non-deviant causation amounts to, yet without such an explanation causal theories are ultimately unsatisfactory.