 Boltzmann brain

The Boltzmann brain argument suggests that it is more likely for a single brain to spontaneously and briefly form in a void (complete with a false memory of having existed in our universe) than it is for our universe to have come about in the way modern science thinks it actually did.It was first proposed as a "reductio ad absurdum" response to Ludwig Boltzmann's early explanation for the low-entropy state of our universe.