Steven Nadler is an expert on the 17th century philosopher Baruch (or Benedict) Spinoza. He was interviewed for the Elucidations philosophy podcast in 2017. Here he talks about Spinoza and free will:

Spinoza had a very idiosyncratic conception of freedom: idiosyncratic because of the larger metaphysical picture in which he discusses the issue of freedom. Remember that for Spinoza, we are all modes, or in God or nature—and so human beings don’t have this kind of ontological autonomy that we ordinarily think that things have. We are no different from other parts of nature….We are governed by nature’s laws, and this is just as true for our states of mind. Our mental states, our emotions, our passions, our acts of volition, our imaginations—even our intellectual thoughts—are all bound together by the laws of nature, just as much as our bodies are.

Spinoza does not think that there is such a thing as freedom of the will, … in any sense in which all things being the same, one could have chosen otherwise than as one did. So if you are looking for the kind of freedom that gives you independence from the causal determinism that governs most of nature, you’re not going to find that in Spinoza. What freedom does consist in, for him, is a kind of spontaneity, or self-governing autonomy. Not ‘spontaneity’ in the sense of uncaused events—there are no such things (for Spinoza) in nature—but, in a way, very much like a Kantian autonomy, where the things you do, the choices you make, the decisions you make, the goals you pursue follow not so much from how you are affected by other things—that’s passivity—but from your own knowledge of what’s really good, and what is in your own best interest….

Maybe the most precise way to put it is: it’s the difference between being acted on and being active. We’re always active to some degree, because we are always striving. That’s sort of our core essence, for Spinoza….

Things strive to maintain themselves. Other things strive to maintain themselves. Sometimes they come into conflict and these strivings push against each other. We as a part of nature are always being impinged upon by other things, and we’re always being passively affected by the objects in the world around us. But because we’re also striving ourselves, we’re in a way pushing back. And so, our lives are a struggle between being acted upon, and being active, or acting. The more free we are, the more active we are. The more we are determined by things outside of us, the more passive we are, the more we are in bondage to the world around us.

So, according to Spinoza, we are only free in the sense that we can do what we want to do, especially if we have good reasons for doing so. This is what philosophers call “compatibilism”, the idea that everything that happens — including human behavior — is caused by something else, yet we are truly free if nobody has a gun to our head and we decide for ourselves what to do.

I think what Spinoza and others call “free will” feels like free will but really isn’t. In order for an action to be free in the purest sense, there has to be a gap between what’s happened before (even the prior state of your mind) and the choice you finally make. You choose to do something – possibly after a great deal of deliberation – but nothing causes you to make that choice, other than your own free will. The result is that you truly could have chosen otherwise.

This is what Aristotle called the “unmoved mover” or “prime mover”. He thought of it as the primary or first cause of all motion in the universe. The unmoved mover moves other things, but is not itself moved by any prior action. To have free will in this pure sense, each of us has to be an unmoved mover.

Are we? It’s hard to believe that we are.