Next Tuesday in my MCCC Logic class I'll again present, as an example of a logical argument, Ward & Brownlee's "Rare Earth" argument against extraterrestrial intelligent life.
1) Complex life is very fragile, and can only exist in a habitable zone.
2) A habitable zone suitable for complex life has many rare earth factors that have come together and appear fine-tuned for complex life.
3) The odds of such factors is astronomical. (That is, of them coming together randomly. If there are other such planets, it would be astounding on the random approach, and would argue for the existence of God.)
4) Therefore, intelligent life probably exists only on Earth and nowhere else in the universe
I'm now thinking of the psychology of alien-belief. Here are some observations from teaching this over the years. Notice the term "some" (not "all") students.
- Most students are interested and engaged in this discussion.
- Some students psychologically need extraterrestrial beings to exist. The very idea that we might be alone feels threatening, in an existential kind of way. (Analagous, I think, to the [for some] demoralizing thought of the eventual end of humanity - see here.)
- I think that, for at least a few students, belief in aliens is a kind of God-substitute. No aliens = no one out there who might contact us, for better or worse. The desire that aliens exist is in inverse proportion to the loss of belief in God.
- When I present this argument in class there is a resistance to it that's stronger than most of the argument examples I give. To logically evaluate Ward & Brownlee's argument is good. But for a few students it seems to go beyond this. This argument challenges a core article of faith for them. They have a kind of religious resistance. To them I have done something scandalous and immoral by arguing that we are probably alone in the universe.
- What if the truth is that we are really alone in this universe? Some, I think, refuse to contemplate such a possibility. It feels bleak.