 It should be noticed that all three of these deficiencies—continence, incontinence, vice—involve some lack of internal harmony. (Here Aristotle’s debt to Plato is particularly evident, for one of the central ideas of the Republic is that the life of a good person is harmonious, and all other lives deviate to some degree from this ideal.) The evil person may wholeheartedly endorse some evil plan of action at a particular moment, but over the course of time, Aristotle supposes, he will regret his decision, because whatever he does will prove inadequate for the achievement of his goals (1166b5–29). Aristotle assumes that when someone systematically makes bad decisions about how to live his life, his failures are caused by psychological forces that are less than fully rational. His desires for pleasure, power or some other external goal have become so strong that they make him care too little or not at all about acting ethically. To keep such destructive inner forces at bay, we need to develop the proper habits and emotional responses when we are children, and to reflect intelligently on our aims when we are adults. But some vulnerability to these disruptive forces is present even in more-or-less virtuous people; that is why even a good political community needs laws and the threat of punishment. Clear thinking about the best goals of human life and the proper way to put them into practice is a rare achievement, because the human psyche is not a hospitable environment for the development of these insights.