Determinism is the view that every event, including human cognition, behavior, decision, and action, is causally determined by an unbroken chain of prior occurrences.
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The two major arguments against Determinism are :
1)The Quantum Mechanical Model
2)The Problem of First Cause
Firstly, I confess
I have not studied philosophy, ever.
While thinking randomly,I stumbled upon the concept of Determinism. I found out that this concept (or similar) already exists in philosophy (Wikipedia \m/), this got me interested in it.
I think my definition of determinism slightly varies from the ones that are usually followed, because it doesn't fail when I introduce Quantum uncertainty in it.
The fundamental question is :
If something is determined (something that is bound to happen) is it wise to say, that it can always be predicted ?
and the answer to the question is NO! , not always
To correctly "predict" an event, one must know all the properties of the system at a given state and also all the rules based on those properties which determine the workings of the system.
And it is next to impossible for man to find all the properties and rules of the universe at any given state, because
he himself is a part of the universe.
So, Quantum theory proves that the position/momentum of a particle cannot be "determined" to an arbitrary degree of accuracy.
I think, here is where most people get confused.
Note that the word "determined" here, means human capacity to comprehend.
The reason for uncertainty in the Quantum Mechanical model is, to observe a particle one needs to throw photons (light) or electrons or something at it, and the study of this photon (which reflects back after hitting the particle) reveals information about the particle under observation.
BUT, as soon as the photons hits this particle, it changes the particle's momentum and position, so by the time light returns to your eye, the position and the momentum of the particle has already changed.
This means that we can never determine (predict) the next state of the universe, because we can't ever find out the correct position and momentum of a single particle.
But this does not mean that the particle does not follow rules, in fact if we eliminated the need to "OBSERVE" we would be right on track.
Which means that given the current state of the universe, the next state of the universe is UNIQUELY determined.
It cannot be predicted because as soon as we try to observe it, the properties we are trying to observe will change.
BUT IT IS DETERMINED.
The universe cannot randomly go to any state it wants.
An example of the application of this concept will be, you reading this post was determined at the time of the Big Bang although it could never have been predicted, but nevertheless the universe could not have gone through any other sequence of states which would have prevented you from reading this post today.
All said, this description still does not address the problem of first cause, but this certainly takes care of all doubts linking determinism to Quantum Uncertainty.