A counter-argument to those who believe no other intelligent life exists in the galaxy is as follows. Any intelligent civilization, like our own human civilization, would be tempted to use any new technology for weaponry against its enemies. It is therefore possible that every intelligent civilization destroys itself before it can expand beyond its own solar system. Given humanity’s own self-destructive technologies, such as nuclear and biological weapons, the history of our own species has yet to show whether or not that hypothesis could be correct.