November 2022Since I was about 9 I've been puzzled by the apparent contradictionbetween being made of matter that behaves in a predictable way, andthe feeling that I could choose to do whatever I wanted. At thetime I had a self-interested motive for exploring the question. Atthat age (like most succeeding ages) I was always in trouble withthe authorities, and it seemed to me that there might possibly besome way to get out of trouble by arguing that I wasn't responsiblefor my actions. I gradually lost hope of that, but the puzzleremained: How do you reconcile being a machine made of matter withthe feeling that you're free to choose what you do?[1]The best way to explain the answer may be to start with a slightlywrong version, and then fix it. The wrong version is: You can dowhat you want, but you can't want what you want. Yes, you can controlwhat you do, but you'll do what you want, and you can't controlthat.The reason this is mistaken is that people do sometimes change whatthey want. People who don't want to want something — drug addicts,for example — can sometimes make themselves stop wanting it. Andpeople who want to want something — who want to like classicalmusic, or broccoli — sometimes succeed.So we modify our initial statement: You can do what you want, butyou can't want to want what you want.That's still not quite true. It's possible to change what you wantto want. I can imagine someone saying "I decided to stop wantingto like classical music." But we're getting closer to the truth.It's rare for people to change what they want to want, and the more"want to"s we add, the rarer it gets.We can get arbitrarily close to a true statement by adding more "wantto"s in much the same way we can get arbitrarily close to 1 by addingmore 9s to a string of 9s following a decimal point. In practicethree or four "want to"s must surely be enough. It's hard even toenvision what it would mean to change what you want to want to wantto want, let alone actually do it.So one way to express the correct answer is to use a regularexpression. You can do what you want, but there's some statementof the form "you can't (want to)* want what you want" that's true.Ultimately you get back to a want that you don't control.[2]Notes[1]I didn't know when I was 9 that matter might behave randomly,but I don't think it affects the problem much. Randomness destroysthe ghost in the machine as effectively as determinism.[2]If you don't like using an expression, you can make the samepoint using higher-order desires: There is some n such that youdon't control your nth-order desires.Thanks to Trevor Blackwell,Jessica Livingston, Robert Morris, andMichael Nielsen for reading drafts of this.
