I just made a post in the forum that I believe is substantial enough to warrant its own discussion. It is a thought experiment meant to disprove "free will"; it is a mind-bending concept for sure, enough so that I spent time unsuccessfully trying to disprove myself thinking there must be something wrong with my logic. But I can think of no other way. Perhaps you guys could let me know what you think, or if you see any failures in this line of thinking.
Defining Free Will
I just devised an experiment to attempt to disprove free will under a physicalist framework. For those that don't know, physicalism is a strong form of naturalism, and it states that the only things that exist in this world should be physical things that operate under the assumption of natural sciences. Regarding the mind-body problem, physicalism would state that mental states, consciousness, etc., are all reducible to underlying physical brain states.
Why is the lack of free will necessary in a world that requires only science to explain? Because without a ghost in the machine, everything in this world would be dependent on cause and effect. It would make no sense for an entity to arise independently of everything before it. To be clear, there is no doubt that actions are generated by brain processes, and the brain could be said to be a part of a person's identity -- that's not what I'm arguing against. What I'm arguing against is the idea that given the same situation, a different result could arise, possibly from a different decision. What I'm saying is everything you've ever done was inevitable and there is no other option. And I have proof.
What We Know
Assuming physicalism -- assuming that the scientific method is the only thing we need to discover how the world works -- we can go a step further and say:
1. Everything in this world is reducible physically to molecular states (or smaller, atomic, etc.).
2. If an external force is applied to an object, the action that object takes is predictable assuming no other force exists.
3. For the conservation of energy to be true, for every action, there is a reaction.
In practice, if I kick the ball in the exact same way, ignoring atmospheric pressures or wind for the moment, the ball will have the exact same trajectory each time. If I press buttons in a calculator, it will give the exact same results. When equal quantities of bleach and ammonia mix, it will have the same chemical reaction each time, assuming the environment is the same. Okay so far?
So for this experiment, first we imagine that if time were frozen in an infinitesimal fraction of a second, there is an exact molecular state representing your body, including your brain, and the environment around you in which you perceive. (If physicalism is true, the only way in which we have access to the external world is through the 5 senses.)
If we make an exact clone of your body at this given time, and feed it a perfect simulation of the surrounding environment at this given time, in a way that could be said that what each clone of the body perceives is the exact same thing, then given that your thought processes must be wholly contained in that molecular state, and that the external forces you perceive is the same, in the next immediate moment, your molecular state will always react exactly in the same way no matter how many times we run this experiment.
And if you object and say: Our thought processes must count for something, maybe they are independent? All we have to do is take a step backwards and examine each slice of time immediately preceding the current time, where you formed those thoughts. Every intelligent entity, like non-intelligent entities, could be reduced to molecular states, as we've previously stated, and a neuron firing an electric signal across synapses is simply a bio-electric, physical response. This action causes a reaction, and is a reaction of a previous action, possibly another bio-electric signal, and we could infinitely regress until the moment of your birth, or further, your conception, your parents' births, the dinosaurs, the Big Bang...
You could also object using a theory of quantum physics to say that there exists a physical property where two possible outcomes simultaneously exist after an observation, but quantum decoherence would also show that the different possible outcomes have no interaction with each other, and in each world, the same actions would result in the same reaction. But more importantly, this does not really object to determinism, not the least because these possibilities cannot be consciously controlled, even if they exist.
And whether you prescribe to naturalist monism or property dualism, which ascribes both physical and mental properties to physical substances, cause and effect affects physical substances directly, so property dualism would not contradict determinism. Mental properties also have no physical interaction and would be impossible to prove using science. For example, it would be impossible to know what mental states a rock has, because while mental properties may be dependent on physical susbstances in property dualism, the physical substance does not change depending on mental properties.
What does all this imply?
Abstractly, that we don't truly have the freedom to act of think as we would like to think we do, and that human intelligence is no different than artificial intelligence aside from magnitude. Practically, it means less than you might think. The law would still be the same, because any action that a person's physical body commits, or habits that are programmed inside his physical body, even if he lacks the ability of will to actually change that, is still attributable to what is understood to be his "identity". So if someone commits murder, it will still be that person's "fault", and it will make sense that a natural reaction to that action is prison. Morality wouldn't exist, but the delusion of its functionality would persist in the same way as if there were free will; people would still continue to impose rules on other people that would help them make sense of their time on Earth, according to whatever arbitrary criteria they choose (e.g. self-survival, or survival of the species, of peace in community, or survival of the fittest, or equality, etc.). The world will largely be the same. In fact that's one of the reasons we can be so sure there is no such thing as free will, because if we imagine if the current world has free will, and if it doesn't, then it will be indistinguishable.