 The PD is usually thought to illustrate conflict between individual and collective rationality, but the multiple player form (or something very similar) has also been interpreted as demonstrating problems within standard conceptions of individual rationality. One such interpretation, elucidated in Quinn, derives from an example of Parfit's. A medical device enables electric current to be applied to a patient's body in increments so tiny that there is no perceivable difference between adjacent settings. You are attached to the device and given the following choice every day for ten years: advance the device one setting and collect a thousand dollars, or leave it where it is and get nothing. Since there is no perceivable difference between adjacent settings, it is apparently rational to advance the setting each day. But at the end of ten years the pain is so great that a rational person would sacrifice all his wealth to return to the first setting.