Kavka’s original version of the puzzle is the following:

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. . . 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.^[1]

A possible interpretation: Can you intend to drink the toxin if you also intend to change your mind at a later time?

• In line with Newcomb’s paradox, an omniscient pay-off mechanism makes a person’s decision known to him before he makes the decision, but it is also assumed that the person may change his decision afterwards, of free will.
• Similarly in line with Newcomb’s paradox; Kavka’s claim, that one cannot intend what one will not do, makes pay-off mechanism an example of reverse causation.
• Pay-off for decision to drink the poison is ambiguous.
• There are two decisions for one event with different pay-offs.

Since the pain caused by the poison would be more than off-set by the money received, we can sketch the pay-off table as follows.