Kavka's toxin puzzle
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Kavka's toxin puzzle is a thought experiment presented by Gregory S. Kavka, a moral and political philosopher, in The Toxin Puzzle (1983). The puzzle challenges the possibility of forming an intention to perform an act which, following from reason, it is extremely unlikely one will actually commit to.
[edit] The Puzzle
There is a toxin which, upon consumption, will make you violently ill for a few hours. You will receive a sizeable lump of money if you are able to intend, at present, to drink this toxin a few days into the future. If the intention is truly and successfully formed, you will be awarded the money without ever having drunk the toxin, and whether you fulfill your original intention or not will not change your reward.
[edit] The Paradox
Now, we need to consider whether or not it is possible to form an intention to perform a future act, given the foreknowledge that after forming the intention you will have no incentive to fulfill your intention. In fact, a person X who attempts this, will have very good reasons not to.
As soon as X intends to drink the toxin, X can collect the reward—X does not actually have to drink it. So, once the time has come to drink the toxin, the reward will already have been collected and the only thing that will result from drinking the toxin will be extreme discomfort—having received the reward, no incentive remains to drink the toxin. Given this foreknowledge, it seems unreasonable for X to drink the toxin. But considering that X can come to these same logical conclusions, X cannot logically form the intention to begin with.
[edit] Non-cognitivism vs. Moral realism
The nature of this paradox is grounded in a non-cognitivist ethical theory, presupposing that there is no objective moral law. In an attempt to deny this paradox, we would need to presuppose a theory of moral realism, in which objective moral truths do exist and we could cite various internal incentives toward the fulfillment of our intention. Examples of such incentives include the guilt that would result from failing yourself by not following through on your intention (to the extent that an intention is a promise made to oneself), or a categorically commanded duty not to lie, including to oneself. Whether or not such an approach would be successful is certainly open to debate, as are the conclusions of the paradox in general. The Thought experiment has also been applied to the compliance problem in contractarian ethics by David Gauthier.
