An individual entirely deprived of context (not that that’s actually possible, but play along here) cannot make a decision of free will because there is no decision that is possible to make; there is nothing to choose from, between, or for; there is no action that can be undertaken, or for that matter avoided.
So a consideration of context is necessary in order to contemplate free will as a possibility, and the existence of context cannot be used to disqualify the possibility of free will or else we’re just talking semantics here.
Determinism implies that one’s actions are caused by one or more aspects of context which may be deemed the causes of the behavior. If I jump every time I’m exposed to red cotton and don’t jump except when I’m exposed to red cotton, then red cotton is totally necessary and totally sufficient, an unusually compelling case for causality.
There is, of course, the possibility that some unknown variable is totally necessary for red cotton to exist but not always sufficient, and that the unknown variable, if tested for, would make me jump, in which case we would say that it is what actually causes me to jump. But as long as we’re playing make-believe let’s pretend that we can just magically know what the causes of an individual’s behavior are, and that we have the equally magic ability to repeat experiments, varying all kinds of other variables and observing the individual’s behavior until we’re all satisfied that, yep, the posited causal variables very dependably elicit the behavior, and in their absence no such behavior is elicited.
I will stipulate that determinism is an accurate description even if the causal variables are very very complex (e.g., huge chunks of history, culture, age, social strata, what was on yesterday’s history final, what the individual’s sister’s pet kitten is names, etc). But if, in order to reliably and dependably elicit the behavior, the causal variable has to be the sum total of the individual’s entire prior lifetime experience leading up to that very moment, that stipulation is erased, because at that point there’s no difference between the causal variable and the individual.
I posit that human behavior is subject to what the “chaos theorist” folk call “sensitive dependence on initial conditions”. In other words, yep, you’d have to repeat every single aspect and element of context to reliably & dependably get an identical outcome in our little imaginary experimental lab. Short of that all you’ll ever get is statistical likelihood.
Those of us who believe in free will — or, more accurately, who find the phrase “free will” to have better resonance and to do a better job of expressing our understanding of action and explanation — when we use phrases like “I did that because I intended to, not because my environment ‘caused’ me to”, the “I” to which we refer is not something we can describe without reference to context, it’s just that it’s also not something that can be accurately described with anything short of the unabridged context, right down to our hormonal and electrochemical state at the moment, our DNA and however it has expressed itself as personality, and the entire chain of events constituting our lives and our memories thereof and the emotions attached thereto.
(I was once incarcerated in an East Texas crazybin where the psychiatrist kept asking me to describe myself but if I referred to anything but me he’d interrupt with “No, I don’t want to hear about your friends, I want to hear about you…no, I don’t want to hear about what you think about ‘society’, I want to hear about you”…until finally I yelled “FINE! My feet are on the ground and my head is in the air!” To my surprise he didn’t say he did not want to hear about the ground or the air…)
If you’re going to say to us, "If you do what you do as a consqeuence of the sum total of everything that has ever happened to you plus everything physical that makes you you as it might impact on personality behavior perception and capacity to behave plus the entirety of all contextual factors that might be impinging upon you at this moment plus the contents of your conscousness including memory and ideation, well, then, hey dude, that’s determinism, … well, I can’t speak for the other people who speak of free will, they might respond differently, for, umm, obvious reasons ;), but I, at least, will say back to you, no, dude, that’s free will.
Which puts us in agreement with regards to everything except what to call it.
If you can’t repeat the experiment in order to demonstrate that I’d again behave exactly the same way without repeating absolutely everything prior to the behavior in question, you haven’t meaningfully distinguished determinism from free will.