Start with this situation:
- Six innocents are drowning: A, B, C, D, E, F.
- One innocent is in no antecedent danger: G.
- Sam, who is truthful but evil, tells me that if I do anything that kills G, he will rescue D, E and F, and only then.
- If I press the green button, A, B and C are rescued.
- If I press the red button, A, B and C are rescued and G is killed along the way (maybe G is standing so close to the relevant drone that he will be killed by the drone when it launches; his death is not a means to the rescue of A, B and C, however).
Suppose first that my choice is between the green button and nothing. (Maybe the red button is covered beneath an unbreakable dome.) Then I should press the green button.
Suppose instead that my choice is between the red button and nothing. Then I should press the red button. My intention would be to rescue A, B and C. The death of G is an unintended side-effect of rescuing A, B and C. The rescue of D, E and F by Sam is welcome but not intended (since if it were intended, then the death of G would have to be intended as a means thereto, and it is wrong to intend G's death).
But now suppose that my choice is between the green button, the red button and nothing. The red button has the best consequences, because two more innocents live. But if I choose the red button over the green button because of this fact, then I am intending the rescue of D, E and F, and therefore I am intending the means to that rescue, namely G's death. To make the point clearer, suppose that the way things work, when I press the green button, a signal gets sent to the drone to go rescue A, B and C, and when I press the red button, that happens and an additional signal is sent to the drone to activate a powerful booster that kills G. To choose the red over the green button seems to involve a choice to activate the booster, since otherwise there is no reason for that choice. Imagine, after all, that one could directly control the two signals without pressing the buttons. It would be wrong to send both the launch signal and the booster signal if one was capable of only sending the launch signal.
So it seems that although the red button is one that it is permissible to press in a binary choice between pressing it and doing nothing, it is not permissible to press the red button in preference to pressing the green button, even though pressing the red button has better consequences than pressing the green button.
If this line of reasoning is correct then to figure out what someone intends one needs to look not just at what they chose, but also at what alternative they chose it against. This fits neatly with my view of our choice and responsibility as essentially contrastive.
But I am not so confident of this line of reasoning.