Kavka’s Toxin Puzzle

A Problem of Sincerity and Retro Causation

Ed Noble
Thoughts And Ideas

--

Photo by 愚木混株 cdd20 on Unsplash

In 1983 the moral philosopher Gregory Kavka presented a thought experiment known as “The Toxin Puzzle”, borne out of his work on deterrence theory. To do it justice, here is the original puzzle as laid out by Kavka:

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.

What is key to this paradox is timing. At the point of drinking the poison, the game will already have played out, with the money either paid or not paid based on whether you passed the intention test. Therefore, we can say that as drinking the poison is inconsequential to winning the million dollars, no rational player would ever do so, given that it is an act of self-harm.

--

--

Ed Noble
Thoughts And Ideas

I write about philosophy, psychology and ethics. I live and work in London, having previously studied physics. Started writing in lockdown.