Thank you very much for the clarifications and for taking the time to write three replies!!! My questions were very important to my maintaining a scientific worldview.
The articles you are posting this week are great!

With much appreciation,
Barry Rucker


(There is a complicating factor of selection bias I’m setting aside here, i.e. we could never be observing a universe that didn’t produce life, so the fact that we are observing a universe already rules out all universes that wouldn’t or didn’t produce life; their probability is exactly 0, in the sense that the probability of the conjunction of such a universe and our observing it is 0, but not because the probability of a lifeless universe is 0. Accounting for that factor is a whole other matter. Google the Anthropic Principle for some discussion of this. I also discuss it in respect to the Fine Tuning argument, using the peer reviewed work of several mathematicians, in The End of Christianity.)

So in answer to your last question: the probability of everything that happens is 100% in the deterministic sense, just like rolls of dice; but that still does not allow us to predict outcomes (any more than rolls of dice).

Because the universe is not infinite in its required state (so far as we know), it is always possible that the initial conditions were such that life would not have arisen even if its arising would be likely, in the same way it’s possible you won’t roll above a one on a six sided die even though that’s likely. Because you don’t actually know the initial conditions and can’t actually calculate whether they will land a one or above a one. Which it is, is 100% guaranteed. But you can only know what’s likely. So you never know what that 100% certain outcome is.

For example, if the universe had been vastly smaller and briefer, we could show that life arising in it has even a total probability of 1 in 10^50 and thus would be extremely unlikely to have arisen in it by chance. But all that means is that of all the possible ways the universe might have been arranged in its initial conditions, only 1 in 10^50 of those arrangements would 100% certainly generate life. Ergo, the odds it will are 1 in 10^50 and not 100%. Not because we can be sure of what those initial conditions were or would be; but because we can never be sure what they were or would be.

Random events are still common on determinism (in fact, most events are random on determinism).

Perhaps you are confusing ontological randomness (e.g. theories of quantum mechanics that reject underlying causes) with practical randomness?

Rolling a die is 100% deterministic. Yet the outcome is still “random,” because we cannot measure all the causes and thus cannot predict the outcome; and because the probability of “a roll” turning up any given number is the same for each number, and though it is always 100% for exactly the same roll, no two rolls are exactly the same.

The same holds for statistical mechanics: atoms in a gas can behave 100% deterministically and yet still will increasingly randomize their order over time, entirely because of their deterministic collisions. Which explains all the laws of thermodynamics. And thus nearly all the observed physics of the universe.

On the other hand, Sense & Goodness Without God–in declaring for determinism (with which I agree)–says, “the course of particles and objects seems determined precisely by mathematical laws that contain no room for spontaneous variation. Everything we see appears to proceed in the one, precise direction it gets caused to go and can go no other way.” (p. 98, paragraph2) Page 99, paragraph 3 refers to chaos theory, in which phenomena “behave in a classically deterministic way, but are so complex that their outcome APPEARS [emphasis mine] quite random.”

Is the solution to the apparent conflict between the above quotations from Why Life Must Be Complex and the determinism in Sense & Goodness Without God to be found in that last quotation from Sense & Goodness Without God (p. 99, paragraph 3)? If so, did the probability of natural biogenesis equal or approach 1, i.e. was natural biogenesis deterministic like everything else we know?

I’m glad that you started there. I get frustrated when someone talks about the possibility of “life” on other planets and doesn’t clarify further.

On a related note I wish everyone would make a habit of doing the same thing when you talk about the existence of God. One of the first principles I learned in Philosophy class (on the subject of the existence of God) is you have to first establish what the person means by “God”. If someone is just a Deist (not tied or bound by any established theological beliefs), there is no point on going down the path of trying to convince them that biblical creationism or a “young earth” is scientifically proved false. I’m not saying that a Deist has a strong case with respect to the probability of their beliefs being true, I’m just saying that there is an additional (vast set) of improbabilities that go along with belief in a religious based doctrine (theological based God), which makes it’s existence even way less probable. Let’s not to thrown the Deity baby out with the theological bathwater.

Because as improbable as complex life on Mars might be, I doubt that it is quite as improbable as finding Marvin the Martian lurking around up there.

And making a scientific argument against the existence of complex life based on the improbability of the latter would not make much sense (regardless of how common or popular a belief that might be).

A more important way that defect may have played out, though:

I think the Martian atmospheric temperature and pressure (and lack of liquid water) are far more destructive of chances of complex biospheres, than the radiation background. And those are relatively recent developments. Mars used to have a warmer, wetter, higher bar environment; and it is that, that its lack of magnetic field could be most responsible for—as solar radiation could then strip away gases and thus drop temp and pressure and hence eventually eliminate liquid surface water.

Alas it’s not so simple as that.

Although losing a magnetic field did substantially reduce habitability, it isn’t strictly necessary. Whole biospheres and even civilizations can arise within the crust, more than adequately shielded from radiation by actual rock.

One also can’t assume life can’t adapt to high radiation environments. We only assume ours is normal; but we are vulnerable to radiation because we haven’t evolved in an environment filled with it. If forms of life can evolve to be resistant to such environments, magnetic fields aren’t so necessary. In aid of this, contrary to predictions, life around Chernobyl has actually thrived despite critically high background radiation. And the radiation levels on Mars are actually not that high. Humans could survive years or decades there even without shielding. So it’s entirely possible species actually evolved under those conditions would survive more than adequately.

And of course, human colonizers would bring radiation shielding with them. And probably in a few thousand years, advanced terraformers will simply magnetize Mars.