Mantus -
The flaw you're looking for in determinism is this:
Every event is stimulated by a cause.
Every cause was stimulated by an event.
Cause -> Event -> Cause ...
This supposes that there had to be either a first "Cause" or a first "Event" from which all other causes and events arose from.
What was the first event? or What was the first cause?
There was no 'first' at all. Free your mind to accept that everything that is, always was. Everything that you perceive as reality - that which is 'happening' is because you CHOSE to experience it.
If that's not free will, then what is?
