Kavka’s toxin puzzle

by James Somers, March 7, 2010

In the January 1983 volume of the journal Analysis, Gregory Kavka presented the following philosophical thought experiment:

An eccentric billionaire places before you a vial of toxin that, if you drink it, will make you painfully ill for a day, but will not threaten your life or have any lasting effects. The billionaire will pay you one million dollars tomorrow morning if, at midnight tonight, you intend to drink the toxin tomorrow afternoon. He emphasizes that you need not drink the toxin to receive the money; in fact, the money will already be in your bank account hours before the time for drinking it arrives, if you succeed. All you have to do is… intend at midnight tonight to drink the stuff tomorrow afternoon. You are perfectly free to change your mind after receiving the money and not drink the toxin.

It’s probably worth asking why this is considered an interesting problem in the first place, since on face there might not seem to be anything difficult going on.

But Kavka seems to think that it would actually be very hard, if not impossible, for someone to intend at midnight tonight to drink a painful poison tomorrow if they knew that they could eventually back out without losing any money. In asserting this he is really taking two steps: first, to argue that a person would never actually drink the poison, because by the time they reach the moment of truth, the prize will have already been won or lost—and no one would choose pain vs. not-pain if all else is equal; and second, to argue that if you knew that you weren’t going to drink the poison tomorrow, there is no way you could intend to tonight.

The first step is fairly sound, although one can imagine challenging it in the following way: suppose that you had somehow managed, last night, to intend to drink the poison today—isn’t there then a sense in which you’re committed to go through with it (such commitment being what initially enabled your intention)? If so, then it may be that to win the money you do have to drink the poison after all. (This was actually the tack taken by philosopher David Gauthier in a paper published shortly after Kavka’s. See the Wikipedia page for more.)

It’s an interesting possibility that cuts to the core of the problem: can someone intend to drink the poison, and if so, what would such a person look like (epistemologically, psychologically)? Would they be somehow bound, Gauthier-style, to follow through, or is there a way to win the money without having to endure a day of pain?

I certainly don’t think it would be the strangest thing to ever happen, and actually I could imagine a few concrete ways you might pull it off:

  1. You could force yourself to literally forget about the option to back out tomorrow. I doubt I could do this, but there must be some people whose minds are sufficiently powerful (or broken) to selectively “delete” memories. (In which case they would in fact follow through and drink the poison, unless the billionaire reminded them that they had the option not to.)
  2. More easily, you could construct for yourself a sort of conspiracy theory in which the billionaire is tricking you, and in which you’ll have no choice but to drink the poison tomorrow. You could get yourself all riled up this way, momentarily terrified by the prospect, but gradually talk yourself down to the point of acquiescence—“there are no lasting effects; it’ll only be painful for a day”—mentally preparing yourself so well to drink the poison that you essentially “forget” about backing out, since that option no longer seems real. This train of thought may sound bizarre, but I’d wager that every day all sorts of paranoid people immerse themselves in far more elaborate fantasies. (And the benefit of pulling this one off is that you would wake up the next day a million dollars richer and amazingly relieved the moment the billionaire let you go.)
  3. You could be one of those thrill-seekers who thinks it would add to your stock of “life experience” to endure a temporary bout of intense pain. (In this case you probably would end up drinking the poison.)
  4. Or you could, quite like a regular person, decide that you really want the million dollars and that you’d be willing to endure a day of pain for it. You might then set out to find some way to intend tonight to drink the poison tomorrow, even though you know in the back of your mind that you are very likely to back out. So for the next several hours you might fight yourself, trying hard as you can to eliminate these nagging thoughts of backing out, flitting back and forth between “totally committed” and “knowing full well I won’t go through with it.” You might even start to consider options like #1-3, but you’d probably dismiss them for being too weird or somehow infeasible. Then finally you’d hit on a brilliant idea: a contract! You have long been telling yourself that “my word is my bond,” that you are trustworthy, that other people might renege or cave but that you always come through. You are certain that if you signed a contract with yourself you couldn’t break it. And so you’d draw one up, sign it, and sleep comfortably, slightly nervous about the day of painful illness ahead, but pleased to know that you’ve got a million dollars in the bag. And it would probably be enough to net you the cash. (Of course odds are that the next day you’d go back on your word, but I imagine we all know a few people who really are so steadfast that they’d actually drink the poison.)

There are no doubt many more methods available. The key point is that human psychology is warpable enough to satisfy the billionaire’s demands—this is, after all, the same psychology that can willingly kamikaze itself in the name of God or country, that is so often ruled by fear and insecurity, that regularly violates expected utility theory, and that acts, for the most part, as though it’s not headed toward an infinite doom.

So the real puzzle here, in my mind, is why Kavka thought this was a “puzzle” at all.