Bayesian Investor Blog

Book Review: Anthropic Bias: Observation Selections Effects in Science and Philosophy by Nick Bostrom

This book discusses selection effects as they affect reasoning on topics such as the Doomsday Argument, whether you will choose a lane of traffic that is slower than average, and whether we can get evidence for or against the Many Worlds Interpretation of quantum mechanics. Along the way it poses some unusual thought experiments that at first glance seem to prove some absurd conclusions. It then points out the questionable assumptions about what constitute “similar observers” upon which the absurd conclusions depend, and in doing so it convinced me that the Doomsday Argument is weaker than I had previously thought.
It says some interesting things about the implications of a spatially infinite universe, and of the possibility that the number of humans will be infinite.
It is not easy to read, but there’s little reason to expect a book on this subject could be both easy to read and correct.
The author has a web site for the book.

Rare Earth : Why Complex Life Is Uncommon in the Universe provides some fairly strong (and not well known) arguments that animal life on earth has been very lucky, and that planetary surfaces are typically much more hostile to multicellular life than our experience leads us to expect.

The most convincing parts of the book deal with geological and astronomical phenomena that suggest that earth-like conditions are unstable, and that it would have been normal for animal life to have been wiped out by disasters such as asteroids, extreme temperatures, supernovae, etc.

The parts of the book that deal with biology and evolution are disappointing. The “enigma” of the Cambrian explosion seems to have been explained by Andrew Parker (see his book In the Blink of an Eye) in a way that undercuts Rare Earth’s use of it (dramatic changes of this nature seem very likely when eyes first evolve). This theory was apparently first published in a technical journal in 1998 (i.e. before Rare Earth).

They often assume that intelligence could only develop as it has in humans, even suggesting that it couldn’t evolve in the ocean, which is rather odd given how close the octopus is to qualifying. But the various arguments in the book are independent enough that the weak parts don’t have much affect on the rest of the arguments.

I was surprised that they never mentioned the Fermi Paradox, which I consider to be the strongest single argument for their position. Apparently they don’t give it much thought because they don’t expect technological growth to produce effects that encompass more than our planet and are visible at galactic distances.

Their concern over biodiversity seems rather misplaced. I can understand why people who overestimate mother nature’s benevolence think that preserving the status quo is a safe strategy for humanity, but it seems to me that anyone sharing Rare Earth’s belief that nature could wipe us out any time now should tend to prefer a strategy of putting more of our effort into creating technology that will allow us to survive natural disasters.

I am disappointed that they rarely attempt to quantify the range of probabilities they would consider reasonable for the risks they discuss.

Stephen Webb has written a book on roughly the same subject called Where is Everybody? that is more carefully argued, but less entertaining, than Rare Earth.