Determinism and free will completely contradict each other and cannot be both true simultaneously.

I probably haven't emphasized myself enough, as it seems that my opponent keeps confusing between the existence of free will as an illusion and the existence of free will as a real property of a living creature. It is important to make it clear and understandable – both theories accept the truth of the sensation of free will. This is something that cannot be denied as we all feel it. However, the question is if free will truly exists or is it just a false sensation we feel? My opponent spoke of two properties of human beings – acting in a non-consistent, although non-random way - and said that those two contradictory qualities gave rise to the concept of "free will". However it remains unclear from he's explanation whether he talks of free will as a real true thing or just as a false sensation. It is understandable that we may never be able to proof one or another, but clearly, it cannot be both true and false at the same time. So, please, Nail_Bat, tell us, do you accept that free will cannot be at the same time both true and false? According to your explanation is free will only a sensation or is it a true property of human beings? Next, I'd like to answer my opponent challenge: "I challenge my opponent to describe a hypothetical scenario in which an agent makes a completely free choice according to the criteria of the definitions he gave." A man is asked to choose a color from a list of ten colors. He chose blue. Why? The determinist will say that he actually had no choice – the fact that he chose this specific color was pre-determined and could be theoretically explained. He will say that there was a chain of causes that led to this specific result, even if we'll never be able to discover them. The fact that we can't reveal them is irrelevant – he only claims for their existence. On the opposite side, the free will supporter will say that due to his metaphysical freedom, the man could choose any color he wanted. Even if he had influences, tendencies, habits or whatever – the man himself is the "ultimate" or "originating" cause of his action. The main difference between those two doctrines is in their answer to the question "Why the man chose that specific color?" – Causativeness for the determinist and metaphysical freedom, making the man the "cause sui" (the cause of itself), for the free will supporter. Both answers can't be true. If we say that the only reason the man chose that specific color is the man himself, we can't say that there was a chain of causes that led him inevitably to choose it. If we say the there was a chain of causes that led him inevitable to choose it, how can we say that he was the originating cause of his choice? Anyway, as Nail_Bat claimed that my definitions led him to some unavoidable ambiguity that can not be resolved unless we choose to frame the issue in one way or another; I'll try to explain how each definition can make it unequivocal. The definition I've used for determinism was "the philosophical doctrine that every state of affairs, including every human event, act, and decision is the inevitable consequence of antecedent states of affairs." According to this definition free will is only a sensation we feel, produced by specific processes happening in our brain. We are deceived to think that we can act freely, however our actions are predetermined and are the consequences of chains of causes. The major problem of this theory, as pointed by Nail_Bat, is the Heisenberg Uncertainty Principle. Nevertheless, we can easily solve this problem, by saying that the principle deals only with the results of the observations and experiments we make. In this case, the world is still deterministic (in the full sense of it – everything is predetermined) but we as humans cannot predict everything in hundred percents. I find it a very coherent explanation indeed. Determinism is not a concept of what we can predict, as Nail_Bat said, but a property of the world itself – claiming that everything is predetermined. If we accept this definition (which I hope became clear and unambiguous) free will is nothing but an illusion. On the other side, the Metaphysical Libertarianism rejects the fact that everything is predetermined and holds onto a concept of free will that requires the individual to be able to take more than one possible course of action under a given set of circumstances – "the power or ability of agents to act otherwise than they in fact do." In this case, free will is a true property of human beings (and of other creatures too, maybe) not just a false sensation. The non-physical theories hold that the choices and actions do not have an entirely physical explanation, so they cannot be determined or predicted because of their own nature (not because of humans' lack of ability). They hold that a non-physical mind overrides physical causality making it prior to the deterministic causativeness, as the cause of itself. Even explanations that do not dispense physicalism, requires at least indeterminism, saying that some events are not predetermined. It seems that the reason for Nail_Bat's ambiguity is his misunderstanding of the implications of the definitions, ignoring their inherent nature, which is clearly unambiguous.