Free Will & Determinism

Determinism - "The belief that a determinate set of conditions can only produce one possible outcome given fixed laws of nature'.

Universal Causation - "Everything that happens or occurs has a cause".

Causal Necessity - "Given the total set of conditions under which the cause occurs, only one outcome is possible".
Example: Water on the Kitchen floor. We look for an explanation as to why it is there, we expect there to be a cause.

Laws of nature are universal - There is no part of the universe in which they don't apply. Therefore every "Physical Event" Falls under the Laws of Nature...
 

Regularity - The use of regularity forms our idea of the laws of nature.

If a burst pipe caused the kitchen floor to become wet, we expect on other occasions that if the pipe bursts the outcome will be the same. leaving the floor wet...

 The concept of regularity leads to the stronger thoughts that, given this cause - in exactly this situation - only ONE outcome is possible. 

These concepts (Universal Causation and Causal Necessity) give us Determinism.

"A determinate set of conditions that can only produce one possible outcome given fixed laws of nature".

The past determines possible future outcomes.

Determinism, then,
                              is the view that given the state of the universe and the laws of nature, only ONE unique state of the universe can occur next.

The Causal Chain - Any physical event is determined by what caused it, its causes were determined by what caused them...

This creates a chain of cause and effect. - A - B - C - D etc.

Any event is determined by what happened in the distant past. Therefore the future of the universe was causally fixed from the first moment, as the first moment determines the second moment thus causing a determined chain reaction.

Physical Determinism - Determinism expressed in terms of physical causes and laws, appeals to logic, this doctrine could be used to explain human actions & choices, in the same way it can be used to explain physical events.

Human Action & Causation. - We naturally accept that our actions are caused. Choices and actions can be explained, as a direct result of motivation, leading to certain events. 

Free Will is threatened by Determinism...
Our actions are events, thefore they have causes. Given the causes they have, no action is possible, other than what we actually do. If we couldn't do any other action, then we do not have Free Will. 

Determinism claims that;
                                              We can predict every event accurately.
                                              Every event is predictable in principle.

We cannot predict events accurately, because we do not know everything about the laws of nature, nor about the 'determinate set of conditions' that leads to a cause of an event. 

If we did, it would be possible for an individual to accurately predict an event. 

Determinism doesn't claim we can know all of a persons mental state/experiences, which allows us to predict with 100% accuracy, it claims that if we knew these factors we WOULD BE ABLE TO.

Predictability doesn't entail determinism.

You may now that if you offer someone prawns or meat, they will choose meat because they don't lie prawns.

Similarly 

You can predict that a friend of yours will help this old lady across the street, because he is a kind person, in a good mood, and he has just said that this is what he will do.

HOWEVER...

These events are not determined, even if they can be predictable. 
Until one can know ALL the conditions affecting an event, predictability doesn't entail determinism. 

Things happening by "Chance" doesn't falsify determinism.

What may seem as chance at one level, can be explained at another level.

Example: You may bump into an old friend by 'chance'. You hadn't arranged to meet, therefore the encounter appears to be a result of chance.

As this encounter IS a physical event, it is subject to the determining set of conditions.
This encounter was a result of determining factors, leading to a somewhat unexpected result.

It may appear to be a result of chance, this event isn't expected. It does not follow the expectations  we form from regularity.

This doesn't mean the event wasn't determined.