does not matter; though they disagree among themselves about what, in turn, does matter. To be a compatibilist, one need not endorse any particular conception of free will, but only deny that determinism is at odds with free will. Although there are various impediments to exercising one's choices, free will does not imply freedom of action. Freedom of choice (freedom to select one's will) is logically separate from freedom to implement that choice (freedom to enact one's will), although not all writers observe this distinction. Nonetheless, some philosophers have defined free will as the absence of various impediments. Some "modern compatibilists", such as Harry Frankfurt and Daniel Dennett, argue free will is simply freely choosing to do what constraints allow one to do. In other words, a coerced agent's choices can still be free if such coercion coincides with the agent's personal intentions and desires. Free will as lack of physical restraint Most "classical compatibilists", such as Thomas Hobbes, claim that a person is acting on the person's own will only when it is the desire of that person to do the act, and also possible for the person to be able to do otherwise, if the person had decided to. Hobbes sometimes attributes such compatibilist freedom to each individual and not to some abstract notion of will, asserting, for example, that "no liberty can be inferred to the will, desire, or inclination, but the liberty of the man; which consisteth in this, that he finds no stop, in doing what he has the will, desire, or inclination to doe." In articulating this crucial proviso, David Hume writes, "this hypothetical liberty is universally allowed to belong to every one who is not a prisoner and in chains." Similarly, Voltaire, in his Dictionnaire philosophique, claimed that "Liberty then is only and can be only the power to do what one will." He asked, "would you have everything at the pleasure of a million blind caprices?" For him, free will or liberty is "only the power of acting, what is this power? It is the effect of the constitution and present state of our organs." Free will as a psychological state Compatibilism often regards the agent free as virtue of their reason. Some explanations of free will focus on the internal causality of the mind with respect to higher-order brain processing – the interaction between conscious and unconscious brain activity. Likewise, some