  Hawking opined that “[i]t seems there is a chronology  protection agency, which prevents the appearance of closed timelike  curves and so makes the universe safe for historians” (1992a,  603). He may be right, but to date there are no convincing arguments  that such an Agency is housed in either classical general relativity  theory or in semi-classical quantum gravity. And it is too early to  tell whether this Agency is housed in loop quantum gravity or string  theory. But even if it should turn out that Hawking is wrong in that  the laws of physics do not support a Chronology Protection Agency, it could still be the case that the laws support an Anti-Time Machine  Agency. For it could turn out that while the laws do not prevent the  development of CTCs, they also do not make it possible to attribute  the appearance of CTCs to the workings of any would-be time machine.  We argued that a strong presumption in favor of the latter would be  created in classical general relativity theory by the demonstration  that for any model satisfying Einstein’s field equations and energy  conditions as well as possessing a partial Cauchy surface  \(\Sigma_0\) to the future of which there are CTCs, there are  hole free extensions of \(D^+ (\Sigma_0)\)  satisfying Einstein’s field equations and energy conditions but  containing no CTCs to the future of \(\Sigma_0\). There are no doubt alternative approaches to understanding what it means for a device to be “responsible  for” the development of CTCs. Exploring these alternatives is  one place that philosophers can hope to make a contribution to an  ongoing discussion that, to date, has been carried mainly by the  physics community. Participating in this discussion means that  philosophers have to forsake the activity of logical gymnastics with  the paradoxes of time travel for the more arduous but (we believe)  rewarding activity of digging into the foundations of physics.