Editing Novikov self-consistency principle (section)

==Implications for time travelers==
The assumptions of the self-consistency principle can be extended to hypothetical scenarios involving intelligent time travelers as well as unintelligent objects such as billiard balls. The authors of "Cauchy problem in spacetimes with [[closed timelike curve]]s" commented on the issue in the paper's conclusion, writing:

{{quote|If CTCs are allowed, and if the above vision of theoretical physics' accommodation with them turns out to be more or less correct, then what will this imply about the philosophical notion of free will for humans and other intelligent beings? It certainly will imply that intelligent beings cannot change the past. Such change is incompatible with the principle of self-consistency. Consequently, any being who went through a wormhole and tried to change the past would be prevented by physical law from making the change; i.e., the "free will" of the being would be constrained. Although this constraint has a more global character than constraints on free will that follow from the standard, local laws of physics, it is not obvious to us that this constraint is more severe than those imposed by standard physical law.<ref name="friedman" />}}

Similarly, physicist and astronomer J. Craig Wheeler concludes that:

{{quote|According to the consistency conjecture, any complex interpersonal interactions must work themselves out self-consistently so that there is no paradox. That is the resolution. This means, if taken literally, that if time machines exist, there can be no free will. You cannot will yourself to kill your younger self if you travel back in time. You can coexist, take yourself out for a beer, celebrate your birthday together, but somehow circumstances will dictate that you cannot behave in a way that leads to a paradox in time. Novikov supports this point of view with another argument: physics already restricts your free will every day. You may will yourself to fly or to walk through a concrete wall, but gravity and condensed-matter physics dictate that you cannot. Why, Novikov asks, is the consistency restriction placed on a time traveler any different?<ref>{{cite book | last = Wheeler | first = J. Craig  | title = Cosmic Catastrophes: Exploding Stars, Black Holes, and Mapping the Universe | publisher = Cambridge University Press  | edition = 2nd | date = 2007 | pages = 294–295 | isbn = 978-0521857147 }}</ref>}}