One of the most striking results coming out of experimental work on people's intuitions about determinism is that people think that a deterministic universe would be really, really, really different from the one we inhabit now. It's not just that it would be different in some subtle metaphysical or moral sense; it's that the whole relationship between people's minds and their actions would be deeply different.
Adam Bear and I wanted to see if we could take research on this topic just one step further, so we tried asking whether people thought there were certain kinds of actions that just couldn't be performed at all if the universe were deterministic. For example, we all know of cases in which an agent was tempted to perform a particular action but then resisted that temptation and did something else instead. We wanted to know whether people thought it was even possible at all for an agent to behave in that way if the universe were deterministic.
To explore this issue, we conducted a study in which each participant was given a description of a deterministic universe and then given a description of one behavior. The participant was then asked whether it would be possible to perform that one behavior in the deterministic universe. Since different participants received different behaviors, we could get a sense of whether the different behaviors led to different judgments.
For each behavior, participants indicated their agreement with the claim that it was possible in a deterministic universe on a scale from 1 to 7. (In other words, the lower the number, the more people thought the behavior was impossible in a deterministic universe.)
Here are the results for a few of the behaviors:
6.06 — Fall in love
5.81 — Have cravings for ice cream that cause them to buy this food
5.13 — Construct complex legal arguments
4.00 — Perform actions that go against the values that their parents taught them
3.69 — Think twice about doing something immoral
2.93 — Suddenly change their mind about what they were planning to do
2.86 — Have the willpower to resist an urge to eat a steak in front of them
In other words, people do think that many of the things we do in our ordinary lives would also be possible in a deterministic universe (constructing arguments, falling in love), but they also think that some of the things we do actually would not be possible if the universe were deterministic (resisting urges, changing our minds).
Clearly, this result is open to a number of possible interpretations, but my sense is that it provides evidence that people regard indeterminism as an absolutely fundamental aspect of ordinary human action. Indeed, it is so fundamental that people think certain ordinary human actions would not even be possible at all if the universe were deterministic.
[If you'd like, you can take a look at our full paper, but please do feel free to comment even if you haven't read it.]