When it's boiled down, compatibilism essentially comes down to how you define your terms and conditions. Terms and conditions that are carefully selected to support the conclusion that free will (a label) is compatible with determinism.
But that's not a fair criticism, because determinism itself also comes down to how you define your terms and conditions. In fact, pretty much every discussion comes down to how we define our terms.
I like to use "operational" definitions when I can, which describe the concept in terms of how it "works" and what the notion is actually used for. For example:
This ultimately fails because it does not take critical factors into account; the nature and role of will, brain function, self and determinism, yet the label is pasted and asserted.
"Will" is a person's specific intent for the immediate ("I will have pancakes for breakfast") or distant ("last will and testament") future. This intent both motivates and gives direction to the person's subsequent actions.
"Brain functions" are the various functions provided by the neural architecture. Perhaps the most significant of these is the organization of sensory input into a model of reality. Included in this model is the "self" and its "internal environment" and also its "external environment". The key brain functions related to free will are imagination, evaluation, and choosing.
"Self" is the brain's model of the person, including things like their body, their thoughts, and their experiences.
"Determinism" is the belief (-ism) that all events are the reliable result of prior events.
"Causal necessity" is the notion that prior events reliably bring about future events, making them necessary and inevitable.
Are there any differences between how we are using those terms?
Again, freedom of will requires human will to have agency in decision making...
"Choosing" ("decision making") is a brain function, available to intelligent species, that (a) inputs two or more options, (b) applies some criteria of comparative evaluation, and (c) outputs a single choice. The choice is usually in the form of an "I will X", where X is the specific thing they will do. That intent then motivates and directs their subsequent actions.
"Freedom of will" refers to the freedom to decide for ourselves what we will do, without meaningful constraints, such as coercion and other undue influences. ("Freedom of will" does not mean a "free floating intent", that is to say, an intent that is not causally determined by the choosing process).
"Agency" is the source of control that brings about some effect.
"Control" is that which decides what will happen next. (For example, my thermostat controls the temperature in my room, but I control the thermostat).
Do you have problems with any of those definitions?
... the ability to change outcome and veto decisions...
The person's brain causally determines what the person will do next. What the person does next determines what happens next. Thus, the person causally determines the outcome.
The person changing or vetoing their own decision would be part of the choosing operation that ultimately leads to the decision. After they've acted upon their decision, it would be too late to change or veto it.
... none of which is permitted by the given definition determinism.
Let's check that. Since "determinism" is the belief (-ism) that all events are the reliable result of prior events, what is the most significant prior cause of a deliberate act? Is it not the act of choosing that sets our intent (our will) upon doing the act?
So, there seems to be nothing about determinism that does not permit a person from choosing for themselves what they will do.
Again;
1. No one has power over the facts of the past and the laws of nature.
2. No one has power over the fact that the facts of the past and the laws of nature entail every fact of the future (i.e., determinism is true).
3. Therefore, no one has power over the facts of the future.
Well, let's think about that.
No one can change the past. But we were active participants in creating our own past. What we choose to do in the present immediately becomes our past. The ability to participate, in actually causing the facts of the past, is our power regarding the facts of the past.
No one can change the laws of nature. But those laws are as much a part of who and what we are, as they are about any other object or force in the universe. We are physical objects, and we are also living organisms, and we are also intelligent species. We are able to imagine many possible futures, to accomplish our biological drives to survive, thrive, and reproduce, and we incorporate the physical forces in our bodies that enable us to bring such futures into actuality. We are not only an embodiment of those laws of nature, but also a force of nature. So, the laws of nature do not require any changes, in order for us to be actual forces of those laws.
1- If determinism allows multiple options to be realized by an agent, as a matter of choice, why call it determinism?
Multiple options are never realized. So, determinism holds. Only one of those option is realized, the one thing that we "will" do. All the other options become "things that we could have done, but didn't".
2- If freedom does not require the possibility of realizable options, that the world proceeds along a determined, singular, course of events, why call it freedom?
The "possibility" of realizing any one of those options is a matter of our ability to realize that option if, and only if, we choose to do so. So, the fact that we did not realize all the options, but only the one we actually chose, does not make those other options "impossibilities", or even "unrealizable", it merely makes them unchosen and unrealized.
"Freedom" is the absence of a meaningful and relevant constraints. For example, the constraints on free speech are censorship. The constraints upon a prisoner are handcuffs and the prison. The constraints upon a free public education is the money usually charged by private schools. The constraints upon freedom of religion is a national religion imposed by the state.
And, of course, the constraints that are meaningful and relevant to free will, to choosing for ourselves what we will do, are "coercion" and "undue influence".
3- If 'freedom' does not require a means for the selection an option from set of realizable alternatves, what is freedom?
Since selecting an option from a set of realizable alternatives is exactly how the deterministic operation of choosing works, we would have to say that determinism in no way contradicts free will, or any other freedom.
Reliable causation is not, in itself, a meaningful or relevant constraint. Only specific causes, like the prisoner's handcuffs, or the cost of a private school, or a national religion, or coercion, or undue influence are meaningful and relevant constraints.
Reliable cause and effect, in itself, is neither coercive nor undue, so causal necessity poses no threat to free will. Only specific causes, such as coercion and other forms of undue influence are meaningful and relevant.
