[...] These situations are all very interesting, and the philosophical consensus is that they are, in fact, logically possible (at least, they are if you buy into the possibility of time travel in the first place!). But how likely are they? If time machines were commonplace, should we expect lots of people to be bootstrapped people, or virtually no-one to be bootstrapped? And why focus on humans? Couldn’t a Tyrannosaur Rex bootstrap itself into existence? And why stop with actually existing things? If time travel were possible you could meet a Wookie that only exists because he’s his own mother and father. Is a Wookie as likely to bootstrap itself into existence as a human? Similarly, if mankind is about to die (and we’re certain time travel is possible) should we expect our time travelling future selves to save us? With the information paradoxes we have the same questions. Is Stephen Hawking as likely as Joey Essex to find his future self telling him how to build a time machine? Am I as likely to meet myself coming from the future telling myself how to build a time machine as I am to meet myself coming from the future telling me how to answer a tricky crossword puzzle?