Should we also avoid reading anything written by Newton or Darwin? After all, they were clearly influenced by all kinds of strange and wonderful religious-based ideas
"Rare Earth", IMHO, is well worth reading; if you don't want to buy a copy, then check it out from your local library. Perhaps I could start a thread, specifically to discuss the approach Ward and Browlee use, the assumptions, etc!
I'll see if there's a copy of Darling's book in my local library, sounds like it could also be a good read.
The article to which Evo gives a link says: "Darling begins with a point-by-point scientific critique of the Rare Earth hypothesis. The hypothesis essentially says that for life to evolve and survive beyond the microbial stage a very special combination of factors must prevail (such as presence of a large moon to stabilize the planet's orbit, a Jupiter-size planet to sweep up killer asteroids, the occurrence of plate tectonics, and a sun with high "metallicity") and that these other factors are both rare in themselves and absolutely indispensable to complex life. Darling examines each in turn and concludes that the hypothesis is based on circular reasoning and that the proponents have fallen into the trap of going out of their way to find reasons why Earth is special.[/color]" Well, I'll reserve judgement on how good a summary of Darling's thesis this is, but as a summary of Ward and Brownlee's, it stinks. For a start, like all good scientists, the Rare Earth authors are at pains to point out the tentative and provisional nature of all their conclusions, so "absolutely indispensable" is hardly accurate.
Next, 'circular reasoning'. Trouble with SETI, and much of astrobiology, is that we have a sample of but 1, so it must surely be nigh on impossible to avoid 'circular reasoning', no matter what thesis is being proposed.
Further, with just this sample of 1, you could always show that personal hopes intrude into one's thesis; they will in Darling's work, and they clearly did in Sagan's (just read the http://www.planetary.org/html/UPDATES/seti/Contact/debate/default.html for a flavour of how one's professional background colours one's views of SETI).
Finally, shortcomings in Ward and Brownlee's work: lots of little ones, and some bigger ones. Perhaps the most glaring - and also the most difficult to overcome, given our sample of 1 - is that they look too narrowly at 'complex life', finding the conditions for it to arise, on a planet just like Earth, rare. But if they'd gone the other way - speculated about how complex life could arise in entirely imaginary planetary systems, for example - they'd have been strongly criticised for unwarranted speculation (and rightly so too; hard observational data on other 'solar systems' isn't sufficient to build any kind of decent case on)
One thing puzzles me though; the SCICOP review says that the Rare Earth hypothesis has been "... embraced by the religious right as vindication of their belief in the special nature of the Earth." Isn't the Earth 'special' no matter what? After all, it's our home. And how does complex life on Earth being rare (if it turns out to be) be of comfort to 'the religious right'? Seems like desperate clutching at straws to me.
