People are literally choosing.
Not if determinism is true. A realizable choice requires the ability to have done otherwise in the same circumstances. Determinism entails no such realizable option, just a determined progression of events.
Necessity:
''Necessity is the idea that everything that has ever happened and ever will happen is necessary, and can not be otherwise. Necessity is often opposed to chance and contingency. In a necessary world there is no chance. Everything that happens is necessitated.''
Primer;
If you accept regulative control as a necessary part of free will, it seems impossible either way:
1. Free will requires that given an act A, the agent could have acted otherwise
2. Indeterminate actions happens randomly and without intent or control
3. Therefore indeterminism and free will are incompatible
4. Determinate actions are fixed and unchangeable
5. Therefore determinism is incompatible with free will
"A realizable choice requires the ability to have done otherwise in the same circumstances."
Correct. A real possibility must be realizable. It must be something that we can actually do, if we choose to do it.
However, it is incorrect to say that, since I have decided that I will not do it, it must therefore be impossible. The fact that something will not happen does not logically entail that it could not happen. The only thing that insures that "it could not happen", is that it is physically impossible to actually do it, even if we chose to do it.
What "can" happen constrains what "will" happen. If it cannot happen, then it will not happen. But what "will" happen never constrains what "can" happen. To say that something "can" happen never requires that it "will" happen. If something "can" happen, then maybe it will happen, or, maybe it will never happen. And when we say that something "could have" happened, it always logically implies that it definitely did
not happen.
In fact, all "real possibilities" exist solely within our imagination. We never think that we can drive our car across the "possibility" of a bridge. We can only drive across an "actual" bridge. And as soon as we actualize our possibility, we stop calling it a "possibility" and begin calling it an "actuality".
But, a possibility that is
never actualized is
still a possibility. And, something that we can do, that we
never do, is
still something that we could have done, even though we didn't.
"Determinism entails no such realizable option, just a determined progression of events."
That is incorrect. Whenever a choosing operation appears in the causal chain, the
determined progression of events will necessarily include at least
two real possibilities (for example A and B), two things that the person "can" choose, even though they "will" choose only one of them.
The arrival of the possibilities, as mental events, are
as causally necessary and inevitable as any other event in the causal chain. The truth of both statements, "I can choose A" and "I can choose B", is guaranteed by logical necessity, because both must be true in order for the operation to continue. If either statement is false, then the operation breaks, and comes to a screeching halt. And, given the survival advantages that come with the ability to choose, it is best not to break it.
The "ability to do otherwise", to be able to choose A and also to be able to choose B, is built into the choosing operation. There will always be at least two "I can's" at the beginning, and at the end, there will always be the single inevitable "I will", plus at least one "I could have, but I didn't".
Necessity:
''Necessity is the idea that everything that has ever happened and ever will happen is necessary, and can not be otherwise. Necessity is often opposed to chance and contingency. In a necessary world there is no chance. Everything that happens is necessitated.''
No problem there, as long as we keep things straight. One of the things that cannot be otherwise, is that, within the choosing event, and, probably within any other mental event that deals with a context of uncertainty, the ability to do otherwise is always true.
Necessity guaranties that it cannot be otherwise.
Primer;
If you accept regulative control as a necessary part of free will, it seems impossible either way:
1. Free will requires that given an act A, the agent could have acted otherwise
2. Indeterminate actions happens randomly and without intent or control
3. Therefore indeterminism and free will are incompatible
4. Determinate actions are fixed and unchangeable
5. Therefore determinism is incompatible with free will
The answer to this little puzzle is that we are the meaningful and relevant
prior cause of the choices that
control our actions.
The final responsible cause of a deliberate act is the act of deliberation that precedes it. And it is we, ourselves, that perform that process of deliberation. As demonstrated in detail above, whenever we perform a choosing operation, the ability to do otherwise comes with it. This satisfies "1. Free will requires that given an act A, the agent could have acted otherwise". So the authors assumption, that we could not do otherwise, is false.
The middle two, "2. Indeterminate actions happens randomly and without intent or control" and "3. Therefore indeterminism and free will are incompatible" are correct. In fact, I personally believe that indeterminism is not present anywhere in the universe. Indeterminism would assert that the effects of a given cause are unreliable. If I press the "H" key on my keyboard, indeterminism would assert that something unpredictable will happen. Perhaps a "G" would appear. Perhaps a Cheshire Cat would appear. Perhaps gravity would reverse.
Determinism asserts that the effects of given causes are reliable. Every freedom we have, to do anything at all, requires reliable causal mechanisms. This includes the freedom to choose for ourselves what we will do. Without reliable cause and effect, we could never carry out our chosen intent. And, if our brains were unreliable, due to a significant mental illness or brain injury, then we would not be held responsible for our actions. Instead, the illness or injury would be held responsible, and would be subject to correction by medical and/or psychiatric treatment.
Okay, I think I've covered everything. Let me know if you think I've missed something.