Earth, Doreen: some more fuel to the fire...
First, determinism on a strict basis means "same inputs = same outputs".
What I refer to as probabilistic determinism (not sure of what philosphers call it) builds in the quantum uncertainty / randomness to the outputs - so that the "same inputs = same probability function for the output" - but the exact ouput is random but obeying the probability function.
With regard choice / freewill:
At a macro level it appears we make choices - that given some inputs we can assess the possible outputs and make a "choice" - exercise free-will. This is all well and good on a macro-level - or so it seems.
But on a micro-level - at the quantum level etc...
We have inputs. We have probabilistically determined outputs.
The output can not assess its own probability function and determine its own outcome - it can not make a choice.
So if individual atoms etc can not make choices... how can you scale that up to the macro and be sure that choices are made?
And just using cause and effect: We have cause. We have (a probabilistic) effect.
A "choice" would be the equivalent of a non-caused agent assessing the various possible outcomes and selecting which one.
But there are no non-caused agents if you think cause/effect hold.
Any "choice" through such an agent that interrupts another cause/effect action to determine the effect is itself an effect of a preceeding cause.
So think of it like this: A causes B or C or D (probabilistic effect).
You, as a person, would like to think that you can assess B, C and D and "choose" which one you want. You choose B.
You, as a person, are now an additional parameter to the cause/effect relationship.
So this is now like A+X causes B.
So what the cause/effect chain actually is would be more like: A causes assessment of B/C/D (which we'll call X) which causes a feedbackloop to result in A+X causes B.
The assessment, X, is also the effect of another chain of cause/effect, with a vast complexity of interconnected feedback loops etc.
And it is this vast complexity that most likely gives rise to what we deem consciousness, and the ideas of choice and free-will.
So if it does not exist at the quantum / atomic level - how can it exist in the macro world? When you examine all supposed "choices" - there are causes upon causes upon causes... and we have actually made no "choice" at all - but our conciousness gives us that illusion - or perhaps our consciousness IS that illusion.