Let’s Just Say That I Want to Believe
Nick Bostrom has a fascinating piece of inductive reasoning in Technology Review called “Where Are They? Why I hope the search for extraterrestrial life finds nothing.”† It’s a thoroughly good read about why it might be reassuring for humanity if we never find evidence of aliens. Bostrom says that aliens have had a very long time to create some kind of evidence of their existence: either they don’t exist or they die out before they develop the right technology.
But what if there is intelligent life on other planets, but colonising the universe in ways that are observable by similar species is what is wildly improbable? This amounts to explaining away Fermi’s Paradox, which is what Bostrom’s essay sets out to confront. Bostrom asks us why we would suppose that intelligent life throughout the universe is a likely scenario in the first place? That the universe is large and old doesn’t imply that civilisations are likely; that we tend to think so is an example of anthropic bias.
The premise of his argument is that a species must pass through a Great Filter (an evolutionary “probability barrier”) in order to colonise space. For humans the Great Filter is either behind us or ahead of us. If it’s in the past then we may be alone in the universe, since the lack of evidence of other civilisations suggests that the formation of life itself has an infinitesimally small probability. If it’s in the future it means the probability is extremely high that intelligent species go extinct before being able to colonise space.
Since Mars is an Earth-like planet, any evidence of life we might find there over the next few decades would indicate that the probability of life forming at all is, in evolutionary terms, not that small. The Great Filter, we might then conclude, is most likely ahead of us. Alternatively, Bostrom argues, no news would be good news, failing to disprove the null hypothesis and increasing our confidence that our descendants may have a chance to realise a space-faring existence.
Reading Bostrom’s piece reminded me of an essay by Clarence Darrow. In “Delusion of Design and Purpose” Darrow debunks the belief that we can infer the universe was designed simply by observing it. Although he didn’t call it as such, Darrow was arguing against a religious anthropic bias. We have a tendency to place ourselves at the centre of our thinking, even when we’re trying to cast our minds outward to the possibility of others. Or, like Voltaire said:
If aliens did not exist, it would be necessary to invent them.
Just as Bostrom is frustrated with those who would welcome signs of life on Mars with open arms, Darrow was annoyed by the tireless certainty of his contemporaries who saw purpose everywhere about them. Both consider the theory of evolution very seriously, and take care to detail its implications. The substantial difference is their level of optimism about what lies ahead. While the former thinks that a lifeless Mars will increase the rational basis of hope in humanity’s future, the latter counsels kindness to one another in the face of existence without reason. The final passage of Darrow’s essay has stayed with me:
The best that we can do is to be kindly and helpful toward our friends and fellow passengers who are clinging to the same speck of dirt while we are drifting side by side to our common doom.
Hey, we may be alone in the universe with less time left than we’d like to think, but at least we’re all in it together. Still, I can’t help wanting to believe.
PS: In case you hadn’t heard, Mulder and Scully are coming back.
† Via Robert O’Callahan.