Abstract

In his article “If Loud Aliens Explain Human Earliness, Quiet Aliens are also Rare”, Robin Hanson proposes the Grabby Alien Hypothesis, which proposes that extraterrestrial civilizations (ETIs) exist outside of our observable universe and are gradually expanding to fill the universe. The existence of such grabby aliens in our future expanding to fill all available niches puts a cosmic deadline on independently originating sources of life. This cosmic cutoff offers an explanation for why human observers seem to be relatively early in spacetime, why the red dwarf stars seem to be inadequate for independently originating life, and why the Fermi Paradox remains unsolved. However, we should worry about Hanson’s proposal, since the Grabby Alien Hypothesis has its own paradoxical implication, namely that most observers in most reference classes should be grabby aliens themselves (Bostrom, 2002). Thus, oddly, finding ourselves not to be grabby alien observers, it seems Hanson is beholden to explain why we are not. Some possibilities for grabby alien observer alternatives can be offered, though none are particularly explanatorily appealing. In what follows, we will 1) attempt to restate in simple terms Hanson’s assumptions, and then 2) reassemble Hanson’s arguments, showing they lead to a paradox, and 3) consider which assumptions should be rejected and at what cost.