Free will and determinism appear to be mutually exclusive.
Einstein’s space-time structure is supposed to be eternal, to have been always there, and to be there forever. Time is an illusion, the great man said. With everything always and simultaneously being there, choice cannot exist the argument runs. Without time the exercise of free will cannot exist. Hundred out of hundred would probably agree. When free will is defended invariably Einstein’s understanding of time is attacked.
There are, however, two ways to understand free will as not necessarily conflicting with determinism, and one of these does not require time and the other only in a much bastardised form.
The first is that free will can be understood as a quality, rather than a function. Free will needs time to serve as a function, that is true. Any concept of ‘future’ must contain a time element, and choices in our normal understanding are inherently orientated towards future effects. So, if by free will we mean that I make a choice today the consequences of which could not be predicted yesterday, then, indeed, Einstein has killed free will, because neither yesterday, today or tomorrow exist. But free will could also be understood as a quality inherent in the result. What is enshrined in the time structure may reflect a result based on free will. The free will element becomes an inalienable part of the result. In the time structure a mechanistic result would thus be of a different nature than a result reached after the exercise of free will. And to the extent sentiments are real, choices, all free, would, correctly, feel different than situations where we had no choice. Results have been there eternally, and results are, in that sense, predictable. However, these results could not have been predicted by an ‘outside observer’ with prefect command of all facts, or by God, because results contain the indeterminate element of being based on free will. That is the difference between pure Einsteinian determinism and determinism allowing for free will. Interestingly, such an allowance for free will within a deterministic universe resonates well with Einstein’s old enemy, quantum mechanics.
The other way of making determinism and free will compatible is based on the many worlds theory of Hugh Everett; a quantum mechanics product. According to the many worlds theory superposition is not followed by quantum collapse but by the birth of a new universe in which the discarded choice is played out. Thus whenever there is choice both options exist in parallel in superposition (Schroedinger’s cat) and according to Everett neither option collapses and each will continue having effect in its own parallel universe. As a result an immense number of universes exist according to the many worlds theory. When you make a choice a parallel you will arise in a parallel universe. A you that is absolutely identical with the you at the time of choice.
The upshot of the many worlds theory is that an unimaginable number of yous live all the possibilities you ever had. All possibilities will be realized in some or other parallel universe. The relevance of this for free will lies in the fact that a you has continuing consciousness throughout all the choices made by that you. All other yous will carry exactly the same experiences and the identical emotional baggage and will have continuing consciousness from the moment they arise. But their own continuing consciousness. All parallel yous will appear indistinguishable from each other, but will not be because each possesses its own unique continued consciousness. If a you dies, for instance, it is little consolation for that you that an almost infinite number of other yous will continue existing in parallel universes. The continued consciousness of the dead you will be no more. This distinction of a specific you from all the other yous is little appreciated by those discussing the many worlds theory, but gives a path forward for assuming free will for any you, since any choice that a you discards will be lived by another you. All universes and all possibilities in a realized form might be forever existing, and thus represent perfect determinism. But a specific you will always have the choice of living one option or the other. The sum of realized options does not change depending on which route a given you takes in a specific situation of choice. Another you will pick up the choice that a given you decides not to live. Thus every you has a thread in her life determined by the choices made. That thread might sometimes be inherited baggage, although not appearing as such. But from the moment of the coming into existence of that specific you the thread of life will be based on the choices, the exercise of the free will of that specific you.
The two above examples are, of course, counterintuitive, yet demonstrate that scientific method and free will must not be opposed. And counterintuitive perspectives are often not counterfactual. After all, our current understanding of the universe was counterintuitive compared both to the geocentric and heliocentric theories.