It hasn't been established that free will exist.
It hasn't been established that an external reality exists. It is certainly true that one can hold (for whatever reasons) that our ability to make choices such that we could have, had we so decided, chosen otherwise, is illusory and that the experience of volition is as well. However, such a view
cannot be based upon
any evidence from any scientific field, because all empirical research (including that purporting to show that conscious choices are unconsciously predetermined) rests upon the assumption that we have free will. In a variety of ways, all experiments rely on the assumption that the researchers could have freely chosen differently than they did. For example, the "random" assignment of participants, samples, etc., into test and control groups in fields as diverse as medicine and nuclear physics or neuroscience and HEP/particle physics is "random" only insofar as the researchers could have chosen different samples, different participants, etc. The "random" assignment is only validly so under the assumption that the researchers could have chosen other than they did by e.g., assigning subject 1 into the control group instead of the test group.
This was always true and was built into the foundations of early modern science in the natural philosophy/physics of Galileo, Descartes, Newton, etc., and has not changed except that it is less appreciate that the only reason classical physics seems to portray a materially reductive, deterministic world is because physics progressed by first assuming one could neglect the observer and then allowing the observer to freely choose the initial conditions of particular systems (also a free choice) in order to determine general laws.
Now, when even this human-oriented pseudo-determinism has broken down, it has become important to quantify just to what extent our ability to make free choices has upon that nature of physical reality (and better yet, how much we loose if we wish to assume that free choice is always illusory).
We can, for example, explain violations of Bell's inequality without even getting into any issues of nonlocality or nonseparability by the assumption of a hidden parameter which determines the choices of the experimenters. The only reason this wasn't leapt upon by theoreticians, experimentalists, and even philosophers of physics as loophole is because by granting such superselection rules, we must allow experiments to be so determined and with this we lose the entire logical validity of any results from any empirical science. Hence statements such as the following:
"all scientific experiments are based on purposeful activity and free will"
Ellis, G. F. R. (). Top-Down Causation and the Human Brain. In N. Murphy et al. (Eds.)
Downward Causation and the Neurobiology of Free Will (
Understanding Complex Systems) (pp. 63-81). Springer.
"Even in physics we cannot exclude the subjective dimension of the human condition. Man’s free will implies the ability to initialize actions, and it constitutes his essence as a responsible actor. We act under the idea of freedom, but the point here is neither man’s sense of personal freedom as a subjective experience nor the question of whether this idea could be an illusion or not. The point is that the framework of
experimental science requires the freedom of action as a constitutive though tacit presupposition." (italics in original)
in H. Atmanspacher (Ed.) (2017)
Knowledge & Time. Springer.
"To test experimentally whether a given physical system is causal, it is indispensable that the experimenter has the freedom
to deliberately choose...Sometimes it is claimed that such a freedom is illusory. Yet, without this freedom all experimental science would be pointless:
To deny the freedom of action of an experimenter is to deny the meaningfulness of experimental science." (italics in original)
Primas, H. (2009). Complementarity of Mind and Matter. In H. Atmanspacher & H. Primas (Eds.)
Recasting Reality (pp. 171-209). Springer.