 We should move, then, to a comprehensive desire theory, according to which what matters to a person’s well-being is the overall level of desire-satisfaction in their life as a whole. A summative version of this theory suggests, straightforwardly enough, that the more desire-fulfilment in a life the better. But it runs into Derek Parfit’s case of addiction (1984, p. 497). Imagine that you can start taking a highly addictive drug, which will cause a very strong desire in you for the drug every morning. Taking the drug will give you no pleasure; but not taking it will cause you quite severe suffering. There will be no problem with the availability of the drug, and it will cost you nothing. But what reason do you have to take it?