Just Like Home

Recently there have been a lot of stories in the news about scientist’s finding water in the atmosphere of an extra-solar planet, and finding an extra-solar planet that they classify as habitable

What is striking (to me) about these stories, besides the overal ‘cool factor’ of space stuff, is that these scientists clearly do not think that life is multiply realized. They are looking for planets of about this size (Earth) with water and land masses (Jupitar is ruled out, Mars is in) and they seem to implicitly assume that life on other planets (if we find it at all) will be simple stuff like bacteria.  Does this represent a serious flaw in their strategy? I don’t think so. We don’t really have any reason, except our imagination and intuitions, to expect life elsewhere in the universe to be other than carbon-based and water dependent. This makes me wonder why philosophers have such strong intuitions about multiple realizability…


  1. Ken Aizawa

    Any interest post on numerous counts.

    There is, I think, often a risk of interpreting what scientists think about rather esoteric philosophical ideas, such as multiple realization. This seems to me to be a case. One might think that water is going to be involved in all cognition, say, but that it is the other realization components that will vary. So, one has to have liquid water for the kinds of chemical processes that we know might sustain life, but thereafter there is much more room for variation.

    Silicone has often been thought of as an alternative for carbon, I suppose, because it has, in some sense, the same valence structure as does carbon, hence that it could give rise to chemical compounds in many respects similar to those that carbon does.

    And maybe scientists are looking for water-using, carbon-based life only because it would be easier to recognize or because finding it would be more certainly life than finding, say, strange configurations of gas clouds of the sort that some philosophers think can multiply realize life.

    So, one has to be careful, I think, interpreting what scientists are up to. Alas, they do not take their scientific agenda from philosophers.

  2. I don’t think they assume multiple realizability is false, but something more practical is going on. Astrobiologists typically study the features of terrestrial organisms and the features of Earth that made Earth conducive to life. Since this is the only empirically grounded case they have to study, to limit their probability of error and narrow their search space, they tend to look for planets with similar properties. But they tend to think such properties are sufficient, not necessary (well, not quite sufficient, but at least increasing the likelihood).

  3. Richard Brown

    Hi Ken,

    Thanks for the comment. I think that you are prob. right, when you (and Eric) say that, at least part of what is going on here is that these scientists want to narrow down the prospects and increase thier chances of discovering what they can definately say is life. But I do not think that this is all that is going on here. I guess I was sort of trying to echo the point made by Becthcel and Mudale that scientists don’t really expect these things to be multiply realized…and if THEY don’t, then why should WE?

  4. kenneth aizawa

    I sensed an affinity between this example of what scientists are supposed to expect and Bechtel and Mundale’s example of what scientists expect.  That is part of what is intriguing about the case.  In both cases, however, I am a bit skeptical of the claims about what scientists expect.  Part of the reason is that I am not sure what to think about cases in which scientists don’t really know or maybe care about some philosophical hypotheses.  This is why, after a (very profitable) discussion with Buddy, I proposed that we “cut to the case” and set aside what the scientists think and consider the scientific evidence on its merits.

    So, suppose that all life does involve water.  That does not show that life and cognitive processes are not MR.  But, there must be more implicit here.  What is the implicit exobiological argument for univocal realization?

    Again, this is a nice item you’ve posted.

  5. Thanks! I think I got the size of the post right on this one! 🙂

    I think you are right in your criticism of B and M and I guess I am willing to grant you your request to skip to the chase.

    But I think there is a way to save their basic intuition if we see that their account of what a brain state is (“activity in the same part or conglomerate of parts of the brain”) is flawed. In my”>https://philosophyofbrains.com/2007/04/12/brain-states-vs-states-of-the-brain.aspx”>my first post I argued that we should construe brain states as synchronized neural activity in a specific frequency. If this turns out to be right, and I think it has a good shot at doing so, then it seems to me that even if you are right about universal localization not entailing universal realization, it will still be the case that two creatures who did not have the exact same arrangement of neurons in a given area could still be in the same brain state. So I don’t think the kind of cases you point to count as cases of multiple realization.

    As for a general exobiological argument, I am not sure what to say. One thing that comes to mind is something like the following. All brained creatures on Earth have evolved to use synchronization in a frequency as a solution to the problem of representation (let’s say for the sake of argument, but I do think there is an arg. for this) then given that Dawkins’ arguments for Universal Darwinianism seem to be good, we should expect that this is a generally utilized strategy by natural selection in the same way that we should expect that eyes would be a generally utilized strategy for solving the problem of extracting information about the enviornment from ambiant light, and the same way we should expect DNA .

  6. I work in a lab where we do neuroprosthetic work (control robotic arm with signals from single units in motor cortex). I think we tend to assume that some of the functions of the CNS and PNS are realizable in computers.

    My work is in sensory processing, and while I think the functions carried out are multiply realizable, it doesn’t affect what I do because I’m interested in how this and similar biological systems work, not in what can be done in general.

    Also, at least one lab has hijacked (with dynamic clamp [an amazing technique, incidentally]) single neurons in simple nervous systems, effectively replacing their relevant electrical parameters with those supplied from a computer model, and their main thesis was that if the (real) network exhibits the same behavior when coupled with its silicon cousin, then their model is supported. This may have implications for all this multiple realizability stuff. I think the paper is ‘Extended dynamic clamp’, and the PI of the lab is Abarbanel.

    A similar undertaking was done by Oprisan et al in “Phase resetting and phase locking in hybrid circuits of one model and one biological neuron”.

    At any rate, it is a mistake to take the scientists views on philosophical matters with too much weight. We tend to worry a hell of a lot about our experiments and data analysis, and are sloppy in our philosophy.

  7. kenneth aizawa

    Hi, Richard.
    Your post raises numerous interesting threads.  There is the appeal to what scientists think.  There is also one that I just posted separately as an aside concerning realization, multiple realization, and levels.  (This touches on your reference to your paper.)  I was hoping to bracket those, althought not kill them, to focus on the exobiological argument that you impute to the scientists.  I can see a kind of Darwinian argument, but I was hoping for an argument that somehow involves water on other planets.  This was the chase I was hoping to cut to.

  8. Richard Brown

    Hi Eric,

    Thanks for the comments. Your lab sounds very interesting (when I was getting my Masters from University of Connecticut, I worked in Chrobak’s lab doing depth recordings of alert and behaving rats). The dynamic clamp does indeed sound like an amazing technique.

    I don’t think that any of this stuff shows anything about multiple realization. It is my understanding that the abarbanel stuff basically uses computers to model the firing patters of neurons and generate synchronized activity with the other neurons. If, as I have argued“>https://philosophyofbrains.com/2007/04/12/brain-states-vs-states-of-the-brain.aspx”>argued, brain states are patterns of synchronous neural firing, then what they are doing is generating artificial brain states, not a different realization at all…

  9. Richard Brown

    Oh,I forgot to say,

    I take the point about scientists and sloppy philosophy (as a philosopher in a lab I saw this kind of stuff first hand), but in their defense, you’d be suprised how often that critisism is true of philosophers as well! But the point that I was making was that we, as philosophers, tend to get carried away by our intuitions about certain cases, and then draw very grand conclusions from those intuitions (Dennett makes a similar kind of point in his recent Carnival article). One way to check this kind of over-reaching by philosophers is by paying attention to what scientists are actually saying. If scientists are sceptical that your imagining a case where their theory turns out to be false is not a good reason to think that the theory is false, then we as philosophers should wonder why we are so impressed by thoses kinds of cases.

  10. Richard Brown

    Oh, thanks for clarifying.

    Let’s see if this is what you were looking for. I think it is safe to say that the attitude towards life generally held by scientists is that it will turn out to be (vergining) on rare. So, we expect to find it, but we don’t expect it to be like star trek. If this is true then I guess we would then expect the conditions under which life emerged here on Earth should be the conditions for life in general.

  11. Eric Thomson

    Abarbanel uses artificial neurons (sometimes implmented in literal analog circuit hardware, sometimes simulated in digital computers) in connection with real neurons in a ganglion in the lobster. I don’t know how the brain states vs states of brains would apply there, but I don’t think it matters. They are implementing certain functional properties of individual cells in silico, nothing new, but by imposing the conductances from the model on an actual neuron, they are effectively replacing the ion channels with functionally equivalent models of the large-scale behavior of the ion channels (i.e., conductance changes). If this isn’t relevant for multiple realizability, then what is? It is a first step toward replacing single neurons with silicon implementations that follow the same dynamics. (Work in neuroprosthetics is even more obviously relevant for MR, though that is complicated by the fact that they tend to take an engineer’s perspective on the brain (i.e., can we get this to work)).

  12. Richard Brown

    Yes, I agree that the neurons are artificial, the point I was making was that if what matters is the pattern of synchronized neural activity then they are not multiply realizing anything.

  13. kenneth aizawa

    Well, I was expecting mention of water in the argument, but that’s not essential.

    I think the property of “being harder than diamond” is not commonly realized.  Things that bear this property are rare.  Still, there seem to be a couple of compounds that have it.  Beta carbon nitride and ultrahard fullerite both have this property and do so in virtue of different patterns of chemical bonds.  Rarity seems to me orthogonal to “plurality of construction techniques”, i.e. multiple realization.

  14. Eric Thomson

    They are realizing neuronal conductances in individual neurons, and these conductances clearly matter. Such conductances are the physiological hallmark of neurons. To talk of patterns of synchronous activity is to switch levels of analysis from the individual neuron to a more system-wide property (and as I said, in the STG of the lobster (and the cortex of vertebrates for that matter), I’m not sure how much this synchrony view will hold up, but that’s an empirical question).

  15. Richard Brown

    Yes, that’s a point well taken…but have you been following the debate in the MR post? I have been arguing that those lower level properties do not matter for the psychological property. What matters is synchronization. And I think the empirical evidence is on my side…but that is indeed another matter

  16. I agree with Eric Thompson that scientists do not rule out multiple realizability; its just that they have seen no evidence that some other etiology besides the history of the Earth can create intelligent life. However, I have heard some scientists talk AS IF they rule out multiple realizability, which is where the poster’s intuition may come from.

  17. Richard Brown

    I was not arguing that they rule it out, but rather that since they do not have any evidience for it (as you also point out) they do not take the possibility seriously; and neither should we

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