Darwinism Design inference Philosophy Religion

Did Darwin Undercut All Paley-Style Arguments?

Spread the love

Recently at Prosblogion, philosopher Alexander Pruss started a conversation off with the following:

Classic Paley-style design arguments go like this: There is some complex biological feature C which is such that

1. God would have good reason to produce C, and
2. C is extremely unlikely to occur through a random combination of elements.

It is concluded that probably God produced C, and hence probably God exists. The standard story is that Darwin undercut Paley-style arguments by providing a plausible explanation that does not involve God.

I shall suggest that the story is not so simple, and that, in fact, a very powerful Paley-style design argument may continue to go through.

Pruss later mentions that he thinks there’s a possible flaw in the argument, but not one due to Darwin. More on that below.

While my point that Darwin hasn’t undercut design arguments stands, there is a serious flaw in the argument I gave, which has not been noticed in the above discussion.

Here’s the flaw. Assume intelligent life supervenes on arrangement of matter. As a dualist, I think this assumption is false, but my design argument shouldn’t depend on dualism (Paley’s doesn’t, after all). In my discussion of option (4) in the original post, I noted that in the classical setting ergodicity by itself yields the claim that almost surely (i.e., with probability one) intelligent life will occur at some time or other. That’s why my explanandum is (5) rather than (4): Why is there intelligent life at t1? But this opens my argument to a very serious objection. I have granted (assuming materialism) that we’re going to get intelligent life at some time or other. Now, if t1 were a randomly chosen time, and we observed that there is intelligent life at t1, then we could use the fact that there is intelligent life at t1 as evidence. But the method by which I came up with t1 was biased–I, who am an intelligent being, chose a time at which I already knew there are intelligent beings, namely the present. So on its face we have here a case of selection bias, akin to that which earlier this fall I was exposing in Rowe’s argument from evil.

Now, I actually think that the argument can perhaps be saved, but only at the expense of controversial epistemology. One method for saving the argument might require thirding in Sleeping Beauty. But all of this is tricky.

Philosopher Joshua Rasmussen chimes in that he thinks the flaw Pruss has identified isn’t as serious as he thinks it is, and in my view the entire discussion ends up being very interesting, though inconclusive.

Naturally, I find the very move Pruss makes interesting – accepting Darwinism and materialism for the sake of argument, and invoking Paley anyway? That’s the sort of thing that should turn everyone’s head.

I offer this exchange up with minimal commentary from myself, since what I find interesting here aren’t any extrapolations we can necessarily draw from Pruss’ argument, but the argument and approach itself. Give it a read and ponder.

Note that Pruss also offered up a similar argument based on the initial low entropy of our universe, for those who enjoy philosophical design arguments.

5 Replies to “Did Darwin Undercut All Paley-Style Arguments?

  1. 1
    vjtorley says:

    Hi nullasalus,

    Pruss’s argument is an interesting one. I’d just like to make a few quick comments.

    1. I prefer to cast Darwin’s argument in a non-probabilistic form. Remember, Darwin himself was a determinist as far back as 1838, as his earlier writings show. Now in Darwin’s day, I think most of his contemporaries would have argued that the emergence of complex life-forms from inanimate matter was not merely unlikely, but physically impossible. Darwin’s argument could be construed as an attempted rebuttal of that argument. What Darwin tried to show was that a plausible pathway existed (random mutation plus natural selection) which, given enough time, could result in the generation of complex life.

    2. I think that there is something to the argument that the emergence of complex life from the Big Bang in such a relatively short time is antecedently very unlikely. There are many more physically plausible scenarios where it takes a lot longer for complex life to emerge, than there are scenarios where life emerges relatively rapidly.

    3. Selection bias doesn’t seem to be such a big problem either. First, instead of asking why there is intelligent life at t1, we can ask why it took less than (say) 100 billion years for intelligent life to emerge. Second, the fact that an intelligent agent is selecting the cutoff point is not a problem if the intelligent agent in question happens not to know the actual age of the cosmos, but knows enough about the way the world works to understand that the emergence of intelligent life from inanimate matter via natural processes is a very unlikely thing, over a relatively short time interval.

    4. What worries me, though, is that Pruss makes assumptions about the antecedent probability of theism: at least 10^-12. He has no basis for that figure, and a curmudgeonly atheist would not even grant him even that, as the concept of God is considered by some philosophers to be logically inconsistent.

    5. Re the assumption that the probability that God would have created intelligent beings that exist at t1 is at least 10^-9: this is a bit odd too. Even to argue that the probability that God would create intelligent beings is higher than under an atheistic scenario, we have to assume some sort of personalistic theism – which I’m fine with, but some theists are not. But I’m very leery of assigning probabilities to God’s making intelligent life by some time t1. What I would prefer to say is that given the laws of our cosmos, and given that we are the only intelligent beings in the cosmos that we know of, I’d expect God to make intelligent beings like us emerge as soon as the conditions of the universe would allow us to survive.

    Got to run now. More later.

  2. 2
    nullasalus says:

    VJTorley,

    Greetings. Some quick comments of my own.

    I think most of his contemporaries would have argued that the emergence of complex life-forms from inanimate matter was not merely unlikely, but physically impossible.

    I admit, this seems off to me. Particularly when we look at the example of Paley’s watch – I don’t recall even Paley arguing it was strictly physically impossible for it to come together by chance, but a question of what we should best infer if we come across a watch.

    4. What worries me, though, is that Pruss makes assumptions about the antecedent probability of theism: at least 10^-12. He has no basis for that figure, and a curmudgeonly atheist would not even grant him even that, as the concept of God is considered by some philosophers to be logically inconsistent.

    If you’re referring to 11/30 reply f from Pruss, I don’t think he’s taking ‘the probability of theism’ there, but ‘the probability of situation C coming to pass given theism’. That aside, though, I doubt Pruss is trying here to come up with an argument that will convert a determined atheist philosopher. But he’s definitely taking a unique approach, since I’m aware of no one else who combines an acceptance of materialism and Darwinism with a Paleyan argument.

    What I would prefer to say is that given the laws of our cosmos, and given that we are the only intelligent beings in the cosmos that we know of, I’d expect God to make intelligent beings like us emerge as soon as the conditions of the universe would allow us to survive.

    This actually has me curious. On what grounds? Even in a strict, literal reading of Genesis that doesn’t take place. (Then again, on such a reading man shows up at most a day or two late.)

  3. 3
    vjtorley says:

    Hi nullasalus,

    Thanks for your reply.

    I would certainly agree with you that people in the nineteenth century would have regarded the chance formation of Paley’s watch as astronomically improbable, rather than impossible. But until about 1800 (perhaps even as late as 1830), the view that the Earth and its various species of living things had always existed was still intellectually tenable. Thus before 1800 one could skirt the “origin problem” simply by saying (as Aristotle did) that human beings have always been here. They didn’t originate.

    Once it became known that the Earth had a beginning, and that geological time was not eternal, the origin of life became a problem that needed to be addressed. Spontaneous generation was still widely accepted, until Pasteur’s experiments dealt the idea a knockout blow in the 1860s, so the origin of simple life did not appear to be such a big deal. If one accepted determinism (as Darwin did), one could also add that it was bound to happen whn it did.

    Complex life was another story, however. Even in the Middle Ages, people realized that the formation of complex animals required a male’s “seed” and that the heavenly bodies alone were insufficient to bring about this process – which is why Aquinas himself recognized that if complex animals had a beginning in time, they must have been produced directly by God. In other words, people thought that while the elements could produce simple life-forms, there was no way they could produce complex ones. They also generally believed that living things always reproduced after their kind. Darwin’s argument can be seen as an attempt to undercut this popular view by postulating a detailed mechanism whereby evolution could have taken place. I don’t know if Darwin himself envisaged his argument in exactly this way, though.

    Regarding the antecedent probability of theism, my evidence that Pruss rates it as at least 10^-12 comes from the following sentence in his argument, where he is discussing the remarkable fact C, that contingent intelligent beings exist, and assessing the probability of C being the case at time t0:

    So P(C at t0|theism)=10^?9, say. Suppose that theism and naturalism are our only options, so P(naturalism)=1?P(theism), and suppose that the prior probability of theism is one [in] a trillion: P(theism)=10^?12 (this is crazy, of course, given the explanatory power of theism). (Emphases mine – VJT.)

    Two comments. First, theism might explain a lot, but that shouldn’t be a factor in evaluating its antecedent probability. Rather, that would affect our revision of this antecedent figure, in the light of relevant evidence (e.g. the existence of complex life-forms).

    Second, a curmudgeonly atheist might be inclined to doubt that the existence of God is even possible – in which case he/she would rate the antecedent probability of God’s existence as either zero or arbitrarily close to zero. To overcome this bias on the atheist’s part, one must point to some fact about the cosmos which requires explanation, according to rationality norms which fair-minded individuals would regard as reasonable, and then establish that God is the only adequate explanation.

    Finally, regarding my comment:

    What I would prefer to say is that given the laws of our cosmos, and given that we are the only intelligent beings in the cosmos that we know of, I’d expect God to make intelligent beings like us emerge as soon as the conditions of the universe would allow us to survive.

    you ask: On what grounds?

    My answer is: given that we are the raison d’etre of God’s making the cosmos, why would God want to wait? If God were to wait, He’d need a reason for doing so – and there could be no conceivable reason for waiting 14 seconds, as opposed to 14 years. So He’d have to make a purely arbitrary decision as to when to produce us. If He’d already decided to produce human beings as soon as terrestrial conditions were suitable, however, then that would be a rational, non-arbitrary decision, which would fit in well with His over-arching goal of producing a cosmos for the sake of intelligent life.

    The Genesis narrative does not contradict my logic: Adam and Eve still had to eat (hence plants had to come first), and humans were made as the crown of creation (hence subsequent to the animals). But notice that they were made on the very same day as the higher animals. God didn’t wait another day.

  4. 4
    nullasalus says:

    Vjtorley,

    Working in reverse here, habit of mine.

    The Genesis narrative does not contradict my logic: Adam and Eve still had to eat (hence plants had to come first), and humans were made as the crown of creation (hence subsequent to the animals). But notice that they were made on the very same day as the higher animals. God didn’t wait another day.

    Sure, but since when does man need higher animals (I suppose vegetarians would say, ‘or to eat animals at all’)? And prior to then birds and fish were present, so even strict vegetarianism wasn’t necessitated. Also, and this one always confuses me about people who talk about God’s intentions – while there’s no doubt on Christianity that God had/has a plan for humans, I think the Genesis narrative also makes crystal clear that God had other interests in mind at the same time. (He calls what He creates ‘good’ at each stage, well in advance of humanity’s arrival.)

    So I suppose part of the problem here is that, yes, God may need ‘a reason’ to delay humanity’s introduction. But then, just how many reasons are we privy to? Job always comes to mind for me when discussing this sort of topic. We can understand some of the plan, but I think a case could be mounted that animals have a part in the plan apart from their direct usefulness to man.

    First, theism might explain a lot, but that shouldn’t be a factor in evaluating its antecedent probability. Rather, that would affect our revision of this antecedent figure, in the light of relevant evidence (e.g. the existence of complex life-forms).

    I’m not so sure there’s such a neat line between explanatory power and evidence, but I suppose that’s one way to look at it.

    To overcome this bias on the atheist’s part, one must point to some fact about the cosmos which requires explanation, according to rationality norms which fair-minded individuals would regard as reasonable, and then establish that God is the only adequate explanation.

    And here I disagree. Attempting to find an argument that can overcome the determined bias of an individual is futile, and not at all a realistic yardstick. How many times have you seen people doubt causality when accepting causality seemed to lead them where they didn’t want to go? How many times have you seen people praise science as a source of truth, then become scientific anti-realists when realism about science led down paths they didn’t expect nor favor?

    To give an example I wanted to address in an upcoming post, when Francis Crick thought that the Origin of Life was too unlikely to occur, he quickly found the existence of manipulative aliens using directed panspermia to be very reasonable. More recently, another biologist happily dove to the multiverse on the same subject. There are already some self-described atheists (even naturalists!) putting forth (ID?) arguments that our universe may be designed by an intelligent civilization (Bostrom’s simulation argument, Gribbin’s multiverse argument, etc.)

    So I think trying to find an argument that absolutely forces any given person to admit to the existence of God just is hopeless. You mention rationality norms and fair-minded people, but establishing a rationality norm or what qualifies as fair-minded will simply invite another argument, and off we spin into eternal debate. My own humble preference would be to supply arguments that at least can support, strongly, that theism is a reasonable belief to hold.

    As for forcing a conclusion, I recall Peter VanInwagen saying that if any topic were ever decisively settled in philosophy by philosophers, it would be a first in the entire history of the enterprise.

    Complex life was another story, however.

    No doubt it was. All I was questioning was the claim that Darwin was working against the view that it was physically impossible for complex life to form. I’m positive Darwin’s theory undercut other ideas, even popular ones – it was that particular one I was skeptical of.

    Edit: I also noticed this: Even in the Middle Ages, people realized that the formation of complex animals required a male’s “seed” and that the heavenly bodies alone were insufficient to bring about this process – which is why Aquinas himself recognized that if complex animals had a beginning in time, they must have been produced directly by God.

    While I don’t want to turn this into a Thomism thread – I think Pruss’ argument is interesting enough, and I want to discuss Thomism and ID in the future – I will ask one thing. If Aquinas believed that, why did Aquinas never make an argument from complexity to God? It seems to me the Paleyan argument was the Paleyan argument because Paley came up with it.

  5. 5
    vjtorley says:

    nullasalus

    I’ll respond as you did, in reverse order. Referring to my claim (in #3) that Aquinas recognized that if complex animals had a beginning in time, they must have been produced directly by God, you write:

    If Aquinas believed that, why did Aquinas never make an argument from complexity to God? It seems to me the Paleyan argument was the Paleyan argument because Paley came up with it.

    Short answer: he did make an argument from complexity to God. You can read all about it in my long five-part reply to Professor Michael Tkacz, entitled St. Thomas Aquinas and his fifteen smoking guns . The relevant sections are in Part 1 of my reply, at http://www.angelfire.com/linux.....l#smoking9 and http://www.angelfire.com/linux.....#smoking10 . To get the full background for these two sections, you might also want to read these two first: http://www.angelfire.com/linux.....l#smoking7 and http://www.angelfire.com/linux.....l#smoking8 .

    One reason why this “complexity argument” doesn’t figure in Aquinas’ main arguments for the existence of God (the famous “Five Ways”) is that the complexity argument assumes that complex animal life had a beginning in time. Aristotelian philosophers in the Middle Ages would have denied that premise at the outset: they believed people had always existed.

    You also write:

    So I think trying to find an argument that absolutely forces any given person to admit to the existence of God just is hopeless. You mention rationality norms and fair-minded people, but establishing a rationality norm or what qualifies as fair-minded will simply invite another argument, and off we spin into eternal debate. My own humble preference would be to supply arguments that at least can support, strongly, that theism is a reasonable belief to hold.

    Perhaps you’re right here. The reason why I’m currently interested in rationality norms is that from my experience of debating atheists, I get a strong sense that the epistemic process whereby they form their beliefs about the world and assess the credibility of new claims is strikingly different from that employed by theists. Perhaps it’s purely because they’re determined to be atheists, but I would be inclined to ask what made them atheists in the first place. Part of the reason (I think) is that they look at the world through a different set of lenses.

    That said, I would agree that Peter van Inwagen’s assertion is factually accurate (so far, anyway), although I do not share his belief that it’s because all philosophical arguments that aim to establish substantive philosophical theses are doomed to failure. I understand he makes this claim in his recent work, The Problem of Evil (OUP, 2006). You can find a good review of the book by William Hasker at http://ndpr.nd.edu/review.cfm?id=9064 (I haven’t read van Inwagen’s book, I’m afraid). At the very least, philosophical arguments can show the “epistemic price” you have to pay if you wish to adopt a certain belief, and for some very exotic beliefs (e.g. denial of the existence of an external world), that price will be so exceedingly high that we might deem it unreasonable.

    Regarding Genesis: I take your point that it’s unwise to second-guess God. I also completely agree that animals have a place in God’s plan, regardless of their usefulness to man. That does not negate the fact that they were made for man, which Genesis teaches. On that score, the mere fact that they can be known and studied by man is enough.

    As to why they needed to be made before man: I have already given one reason, not related to diet (humans, as the crown of creation, should come last), but here’s another, which takes as its starting point the assumption that God wants us to understand ourselves. Human beings are chordates – in particular, vertebrates. They are also mammals. On top of that, they are primates. I could go on, but my point is: we could never make these classifications (and hence understand ourselves properly) if other animals in these categories did not exist.

Leave a Reply