While the article didn't mention it, free will is a problem for theists too - even more so in my opinion.
An omnipotent being who has perfect knowledge of the future already knows what you'll do. There is no wiggle room in there for you to make a 'different' choice.
> We have, it is widely believed, the power to think, choose, and act in some crucial respect independently of those causal factors that create us as persons, and that surround us each moment of our lives. Unlike anything else in nature, human beings have a special contra-causal freedom to cause things to happen without themselves being fully caused in turn.
I'd still like to hear a believer's definition though.
Thanks for digging out that definition. Alas, the author has inadvertently presupposed the existence of agents with free will by the very way they phrased it. Let me try to explain, without creating too much of a wall of text.
For one thing, it uses the language of cause and effect. Bertrand Russell was the first to point this out: the language of cause and effect is not the language which physicists use to describe reality. Consider F=ma. You might be tempted to say that the force is causing the mass m to accelerate at a rate of a; after all, if I were to vary the force, I will vary the acceleration. But if you vary the mass you'll vary the acceleration too: is the mass the cause of the acceleration?
And notice what was just said: "if I were to vary the force..." i.e. you have introduced an agent. And you have spoken counter-factually about this agent: the agent could have chosen to vary or not to vary the force. I.e. using the language of cause and effect presupposes that an agent is the cause, and has the choice to cause or not to cause. Using the language of cause and effect to describe a physical situation is ultimately an anthropomorphisation.
Cause and effect are part of what Dennet calls "the intensional stance" i.e. the language and vocabulary which we are forced to use when describing the behavior of intensional agents. In order to at all make an intensional agent's behavior understandable, we have to treat them as uncaused causers. When courting a spouse, or raising children, you quickly learn that people cannot be treated as deterministic, stimulus-response mechanism. You have to presuppose that they can freely choose how to react to you.
The question of whether or not we have free will is therefore, not a question of whether we have to presuppose that we have free will; we do. Its just a question of whether the language of the intentional stance is merely a useful heuristic.
But arguing against free will by invoking the language of cause and effect, as the above definition does, is a category mistake, akin to arguing that 1 + 1 can't equal 2, because green + green equals green.
> Alas, the author has inadvertently presupposed the existence of agents with free will
The existence of agents, not the existence of free will.
> For one thing, it uses the language of cause and effect ... is the mass the cause of the acceleration?
Completely irrelevant.
> In order to at all make an intensional agent's behavior understandable, we have to treat them as uncaused causers.
Since your argument feels like 'language games' in places, let me play one too: "We have to treat x as y" strongly implies that x is not y, but it's useful to pretend that it is.
> And you have spoken counter-factually about this agent: the agent could have chosen to vary or not to vary the force.
"Could have chosen" is like a coin which "could land on one side or the other". Not knowing the outcome of the coin flip is no reason to suggest the coin had a choice. Likewise with more complicated devices. From simple open-source programs, to programs whose source code you can't see, to a set of pre-trained weights embedded in an LLM mimicking neurons, to neurons themselves, automata become harder and harder to predict, but there's no cutoff after which an input-output device becomes qualitatively different. We are soggy meat responding to measurable electrical signals.
> But arguing against free will by invoking the language of cause and effect, as the above definition does, is a category mistake
If not cause-and-effect, what exactly do you propose 'free will' is 'free' from?
Free will is the ability of an individual to take actions that are independent of an individual's construction (that what made the individual what it is) or any external stimulus (something motivating the individual to act or not act).
There is no free will. Proof: there is no possible source of free will, so it doesn't exist.
Whatever free will is, this can't be the definition of it. Consider two computers, build for one and only one purpose: to compute the first 10 digits of pi. They do this without any external input. But one computer is made of vacuum tubes, one made of transistors, both of which computed the first 10 digits of pi.
They both took the same action (computing the first 10 digits of pi) and it was independent of how they were constructed, and absent any external stimulus. Yet they don't have free will.
Its harder than it looks to define free will; I'd encourage you to try again.
Perhaps I did misread it. Let me try again. Your proposed definition is not adequate, because if something were constructed to have free will, then it would be exhibiting free will because it was constructed that way :-)
You first have to show that it is impossible to construct something in a way that it has free will. To show that, however, I think you'd need a definition of "free will" which is not "doing something it wasn't constructed to do" on pain of either circularity or contradiction.
An omnipotent being who has perfect knowledge of the future already knows what you'll do. There is no wiggle room in there for you to make a 'different' choice.