Your interpretation of free will does of course dictate whether or not you can believe in Determinism.
Personally I believe that free will exists insofar as that we are physically able to do anything we want, however what we "want" to do (i.e. the decisions we make) is predetermined. In answer to the replies:
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This is reasonable, though I am skeptical of the claim that it is only possible for an individual to make one decision in any situation. If free will exists at all, then determinism must be absolutely false. If determinism is true, then free will is false. However, can all possible choices be known to us, or can we only know our selected choice/determined action?
Allow me to provide an example. Say that I am exploring a cave, and the cave should come to a fork of 78 prongs. These 78 forks have the exact same physical conditions, from light distribution to temperature. Am I determined to select a specific route based on determinism? If so, why?
We can discuss determinism in the wake of solipsism once we've negotiated this crevice.
In response to your "78-prong" example, regardless of the conditions you are in you will still make a decision in the end - you won't just stand there, unable to move for lack of any perceived differences in the options. In that particular situation the path you "choose" will be the one that most suits your inherent personality, therefore still supporting my theory that we make our decisions based on predetermined logic paths in the brain.
For example, as a general rule people will always go for a more moderate route in the absence of other deciding factors, meaning that you might choose a more central path - this is particularly relevant when making a snap decision. Conversely, you may think about it logically and decide to choose the leftmost or rightmost path, depending on your personal preference, meaning that if you need to retrace your steps later on you'll be less likely to lose your way.
Regardless of the choice you make, it'll still be the result of your internal processing.
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Personally, I'm a great supporter of free will. In my opinion, no decision is right or wrong, as long as you fully support your own decision AND don't hurt other people with it.
For example, in later life you have to choose what you want to do. You have the option of becoming an artist or a high-rewarding job as a manager. Neither of these choices are wrong, as you should do what you want to do. Of course there are always people that tell you your choose is actually based on what you can do better. IMO, that is partially wrong.
For instance, I'm good with biology and chemistry. I could easily choose to do something in later life with these two, as right now in the Netherlands, there is a shortage of people with this knowledge. So, why did I choose to pursue History? Because I wanted to.
This is all of course my view on life, if you disagree, you are perfectly allowed to disagree. It's a free world.....or at least it should be.
Similarly to my other response, this doesn't actually disprove the idea of determinism. Whatever decision you actually make will still be the result of your internal reasoning based upon your previous experiences and how they have affected your personality.
Every decision everyone makes is the "best" decision they can make at the time, based upon the knowledge they have available to them as processed by their brain. Regardless of the decision made it's still the result of our inherent determinism, as whatever our "best" decision is at the time we will still have come to that conclusion through our brain's processing of our surroundings.
The theory doesn't necessarily negate free will, all it requires it a slight re-interpretation of what we perceive free will to be. If free will is interpreted as the ability to come to any number of conclusions based upon our personality (i.e. our internal logic paths) without limits to the possible results, then free will and inherent determinism can still coexist.
One way to look at it is to see the theory as an explanation of
how we make the decisions that we make. The only way to disprove the presence of this inherent determinism in our decision-making processes is to prove the existence of a person's "soul" - that is, some overarching decision & personality structure that influences our decisions independently of our physical brain. Without that external influence to our decisions, we are simply machines.