It is the necessity of determinism that negates choice and the notion of free will.
Actually, it is the necessity of determinism that guarantees that choosing will be happening and that we will be doing it.
Universal causal necessity/inevitability doesn't actually change anything. The feeling that you're experiencing, that you must be free of cause and effect in order to be 'truly' free, is a delusion.
Every freedom that we have, to do anything at all,
requires reliable causation. We are not merely the effect of prior causes, but also the causes of new effects. And, because we are members of an intelligent species, we actually get to choose what effects we will cause to happen.
When a person gets to choose for themselves what they will do, it is called "free will". And people will be held responsible for what they deliberately choose to do. For example, in the restaurant, you will be billed for the dinner you ordered.
What is necessarily done is not freely chosen from a set of realizable alternatives, because none of the alternatives are realizable in any instance as the system evolves without deviation.
Freely choosing what you will order for dinner, from a literal menu of realizable alternatives, is
exactly how events evolved in the restaurant.
Everything necessarily happened exactly as we experienced it happening, without deviation.
Pretending that these events did not happen as we observed them happening would be a self-induced hoax. A trick you're playing upon yourself by the words you're choosing to describe them.
If alternate actions were possible, there would be deviations and the system would not be deterministic.
Alternate actions are "possible", but there is no "actual" deviation from the necessary course events. If you can ever get it straight that a possibility is not an actuality then this should clear up for you.
The fact is that there are multiple "possible" futures but only one "actual" future. Within the domain of human influence, the single actual future will be chosen by us, from among the many possible future that we will imagine. (We cannot account for events outside our domain of influence).
However, as we are talking about determinism, there can be no deviation in what is a singular progression of events....hence no choice and no free will.
There "can" be deviations from the singular progression of events, but there never "will" be. If you can ever get it straight that what "can" happen is different from what "will" happen then this too will be clear to you.
The definition of free will as acting according to one's will, without external coercion, force, etc, fails to prove it's proposition because it ignores internal necessity.
The simplest example of "internal necessity" is choosing for ourselves what we will do. When we decide that we will do something, it sets our intent upon completing some task. That intention (also called our "will" or even our "will power") motivates and directs our subsequent thoughts and actions as we go about completing the task. After we're done, we decide what we will do next.
When we are free to make that choice for ourselves, specifically free of coercion and other forms of undue influence, then it is commonly known as "a choice of our own free will". But if someone or something forces us to do something that we would rather not do, then we are not free to make that choice for ourselves, thus not free will.
Inner necessity arises from our own needs and desires. As an intelligent species, we get to choose how we go about satisfying those needs and desires. When faced with the restaurant menu, many thoughts and feelings may come to mind. Our dietary goals, our taste preferences, the relative cost of different meals, what he had to eat earlier in the day, etc., may all play a part as we compare and evaluate different choices. All of these things are a part of who we are, and our own thought process will inevitably lead to a single choice. This is what "inner necessity" is about. It is something we are all familiar with, because we've all made decisions before.
Inner necessity is nothing more than who and what we are. It is not some external agent forcing us to do something against our will, but rather how we construct our own will to meet our own wants and needs.
That what is thought, felt and done, is done not through choice or free will, but necessity.
Incompatibilists present themselves with a false dichotomy, "either necessity or choosing, but never both", hence incompatibilism. That error blinds them to what everyone else objectively observes to be happening in real life.
The compatibilist sees the choosing necessarily happening within a deterministic world.
Necessity does not equate to free will, hence incompatibilism.
Universal causal necessity includes all events. There are events in which a person is free to choose for themselves, as well as events in which someone else's choice is forced upon them against their will. The notion of "free to choose" only requires freedom from coercion and undue influence. It does not require any irrational freedoms like "freedom from cause and effect".
That's all I have time for.....plus there is a tag team of four compatibilists now.
You should try Reddit then. Over there the incompatibilists have a significant majority. So, I know how your feel.