The main thesis of this dissertation is that free will, if understood as a thesis about control over alternative possibilities, can be plausibly formulated only in an indeterministic world. An empirically sensitive conceptual analysis has been adopted as the methodological framework within which such a thesis is formulated. Such an analysis can be criticized from two separate philosophical standpoints: the negative program of experimental philosophy and the work of naturalistically inclined philosophers who believe that several questions formulated within the free will debate are metaphysically irrelevant. I have tried to show that these criticisms are ill formulated and cannot prove what they purport to prove. In order to prove the main thesis of this dissertation, I hold that several aspects of the compatibilist approach are unacceptable. Namely, by relying on the consequence argument, I argue that it is implausible to suppose that one can act otherwise in a deterministic world. I also find unacceptable the idea that freedom, conceived as control over the production of actions, is compatible with determinism. Using the prior-sign dilemma defense I respond to Frankfurt‟s criticism of the principle of alternative possibilities and, by doing so, I defend the idea that our practice of holding someone morally responsible can be safely grounded in the possibility of deciding to act otherwise. In order to justify the application of a libertarian approach to the conception of freedom as control over alternative possibilities, several problems inherent to that approach have to be addressed. I argue that indeterminism should not be considered as a threat to free will, rather it should be regarded as constitutive of our ability to decide to act otherwise. I reject the approach to libertarianism that relies on special forms of agent causation and approaches that remain silent on the issue of causation of decisions. Therefore I defend the idea that the only available libertarian approach which can guarantee control over alternative possibilities is one that is formulated within the theory of event causation.