On deviant causal chains - no need for a general criterion

Donald Davidson brought to our attention deviant causal chains as a problem for causal theories of action. Consider Davidson's own example: A climber might want to rid himself of the weight and danger of holding another man on a rope, and he might know that by loosening his hold on the rope he could rid himself of the weight and danger. This belief and want might so unnerve him as to cause him to loosen his hold, and yet it might be the case that he never chose to loosen his hold, nor did he do it intentionally. (Davidson 1980: 79)