The other day I finished reading Sam Harris's "Free Will." It's a delightfully short book; it's not too hard to get through in the latter half of a day. I recommend it highly, but I think I can communicate my position on free will, which is similar, in even fewer words. Here goes.

Reality can be described at two different levels of abstraction. There's the "human world" where it makes sense to talk about ordering pizza and taking the dog for a walk. There's also the "particle world" where it makes sense to talk about atoms, electrons, fields, wave functions, and maybe strings. As a materialist, I see the "human world" as emerging out of the "particle world." If you aren't a materialist, just rename "particle world" to "particle + magic world" and you'll still be able to make sense of what I'm about to say.

A person's actions in the "human world" correspond directly to events in the "particle world." For example when Timothy Loehmann killed Tamir Rice, his actions corresponded to the movement of a finger leading to the activation of an exothermic reaction accelerating a mass of metal through a barrel towards Tamir. In principle, we could describe what happened in terms of all the particles and forces involved.

For any action a person takes in the "human world", you can take out your microscope and look at it in the "particle world." From there you can trace backwards in time to see the tree of things that caused it. If you're a dualist, just keep tracing backwards into the soul, following (backwards) whatever rules you have for converting changes in soul-states to changes in physics-states. Thinking this way turns free will into an empirical question: What are those causes, and which ones are most significant?

If we looked for the answer to this question, what could we possibly find? The best way to imagine what we could find is to consider three imaginary universes, and then to recognize that reality is some combination of these three. I'll call them Imaginary Universes I, II, and III.

In Imaginary Universe I, our actions depend on past physical events which themselves map back up to the "human world." This means that all of our current actions in the "human world" are determined by past events in the "human world" and nothing more. The information is communicated through the "particle world" but other than that the "particle world" doesn't matter. In this universe it makes sense to talk about, for example, a rapist who raped because they themselves had been raped as a child.

In Imaginary Universe II, things that are meaningful in the "human world" are insignificant to our future actions. Our actions arise out of physical processes that are not tied to any human-meaningful things. For example, a brain might measure the cosmic rays passing through it to make decisions, and so every decision made in the "human world" corresponds to some supernova going off billions of years ago. Here, the pizza delivery guy didn't show up because I ordered pizza, he showed up because some totally unrelated space event made his brain decide he should come to my house with pizza.

In Imaginary Universe III, the world outside of our brains doesn't matter at all to our decisions. When we're born, our brain is endowed with an initial configuration, and that configuration evolves over time, uninfluenced by any of our sensory input or anything else that's going on in the world. It just blindly decides what our next actions will be.

The world we live in isn't anything like these imaginary universes. But if we do the experiments and trace back the causes of all of our decisions, we should find they fall into some combination of these categories. We might find that some kinds of actions, like all kinds of "getting revenge" are a lot like Imaginary Universe I. Other actions, like a mathematician writing a proof, have their recent causes coming from Imaginary Universe III.

When you're thinking about free will, don't just ask "Is free will real or an illusion?" and what the answer means to ethics. Inquire about the results of the above-hypothesized experiments and what they would mean to ethics. Also, be careful how you define "you."