New Paper in Draft: Substrate Flexibility and the Copernican Principle of Consciousness
with Jeremy Pober
Given the surge of interest in AI consciousness, the issue of “substrate independence” or “substrate flexibility” is now a hot topic in the metaphysics of mind. That is, does being conscious require having a particular material composition? Or can anything with the right type of functional structure and behavioral sophistication be conscious, regardless of what it’s made of? Biologicists say that biological details are crucial. Functionalists say those details don’t matter, as long as the right high-level functional organization is present.
Jeremy Pober and I offer a new angle into this issue, drawing on our “Copernican Principle of Consciousness”. The core idea is that it would be strange -- a violation of a type of Copernican mediocrity -- if among all of the many behaviorally sophisticated species that have presumably evolved in the universe, somehow only we with our particular biological substrate are conscious. Since it’s plausible that some of these other conscious organisms employ substrates different from our own, we should allow that consciousness is “substrate flexible”: It does not depend on having our particular substrate. Whether we can generalize from such biological substrate flexibility to the possibility of consciousness in as different a substrate as computer chips... well, that’s a complicated and uncertain issue, on which Jeremy and I diverge in the penultimate section of the paper.
---------------------------------------------
Substrate Flexibility and the Copernican Principle of Consciousness
Jeremy Pober and Eric Schwitzgebel
Abstract: We present a novel argument for the substrate flexibility of consciousness -- that is, for the idea that conscious experiences can arise in a variety of different types of physical media, not just in biological animals as they currently exist on Earth. Some recent critiques of standard arguments for the substrate flexibility of consciousness (e.g., Cao 2022; Block 2025; Seth forthcoming) have emphasized that humanlike consciousness might require our specific biological substrate. However, such critiques are too narrowly focused to address the issue of consciousness in entities whose experience may be very different from ours, for example alien life forms or future AI systems designed along unfamiliar lines. Given that it’s likely that functionally complex, behaviorally sophisticated entities have arisen or will arise many times in the observable universe, in diverse substrates, we argue that it would be a violation of a principle of Copernican mediocrity to hold that among these diverse entities, only we, or only we and a small proportion of others who share our substrate, are conscious.
Full draft here. As always, comments welcomed, either here, by email, or on my social media
.
I'm reading the article and while I agree with the premises in general they are hard to justify objectively. It seems likely there are lots of other intelligent and conscious minds out there in the universe instantiated in very different physical systems but isn't that just assuming the very point we're trying to claim? Don't those estimates of technologically sophisticated alien civilisations smuggle in the assumption by the back door? Similarly, talking about there being - in theory - different chemical recipes that *could* have given rise to human life and consciousness is also based on an assumption - after all you can't point towards any such systems that actually exist. So it is all *plausible* but seems to hinge on assuming something that *I* think is likely but is not accepted by those you're arguing with. I also think arguing Copernican Principles vs Anthropic Principles is a losing game - the Copernican seems more likely to me but many others are just as convinced by arguments about physical constants so it clearly isn't decisive.
Essentially it all seems to come down to who you think has a duty to prove or disprove which position - and that's where each side is forever separated. Not on the facts but on the a priori intuitions. Just as I don't think it is particularly likely that small differences in calcium gradients is going to make much functional difference when swapping out a biological neuron with a mechanical one apparently you find that argument convincing. We have no evidence one way or the other. So the arguments seem fairly unhelpful which is probably why you end up differing on the most relevant question - that of AI consciousness - because you're arguing in a vacuum - about whether a thing you can't define can be realised in different substrates through mechanisms you also can't identify. It seems like an argument designed to draw out priors rather than settle the question.
I haven't read the full paper yet, so this obviously has to be taken with a mountain of salt, but the argument (mostly as summarised in the abstract and post, although I have skimmed!) strikes me as an odd hybrid of a priori and empirical reasoning that needs more empirical evidence to be credible. I don't mind speculation in philosophy, obviously, but this almost seems too speculative!
Here's an early move that confuses me. You write:
"Cosmologists and astrobiologists generally estimate measurable characteristics, among which are 'technological civilization' and 'technosignatures' (Frank and Sullivan 2016; SETI 2021; Wright et al. 2022). The idea is that an alien civilization with technology like our own is potentially observable, for example if it broadcasts radio-frequency signals or builds observable megastructures, such as a gigantic habitat or energy collector around a star.
"How common are technological civilizations? While some astrobiologists think it’s possible that Earth contains the only one in the approximately one trillion galaxies that currently form the observable portion of the universe, estimates are typically several orders of magnitude higher than that (e.g., Frank and Sullivan 2016). One recent survey found median scientific estimates over one civilization per galaxy at some point in that galaxy’s lifetime (SnyderBeattie et al. 2021)—low enough to explain the “Fermi Paradox” (the question of why we haven’t yet seen evidence of technological civilizations) without making technological civilizations extremely rare. For purposes of the present argument, the existence of at least a thousand technological civilizations scattered in time and space across the observable universe—one per billion galaxies, or 0.000000001% of the median scientific estimate—is more than sufficient; we adopt this extremely conservative estimate.
"Developing a technological civilization is related to what we call behavioral sophistication. ..."
The first paragraph I quoted strikes me as an odd fit with the rest. How do these two paragraphs connect? It seems like the second paragraph needs to be about how these measurable characteristics have been observed. But have they? You move from presenting a standard of evidence for alien technological civilisations to a survey of astrobiologists estimating the probability of alien civilisations, but the implication is that these astrobiologists are not relying on the standard of evidence you opened with and instead base their estimates on something else. If that's so, why mention the technosignatures standard of evidence at all? It seems like you're about to say these have been observed, but then you imply they haven't, since you don't confirm that. If technosignatures have been observed, why not mention that in the next paragraph, instead of citing surveys which otherwise rely on unknown reasoning?
Basically, once you bring up the technosignatures, it seems like you next need to say "and we have observed these." Then, you would be on pretty solid ground for beginning your case. If you bring them up, and actually, we haven't observed these, shouldn't we count against your argument? If so, why not acknowledge that strike against you and then move on to the surveys as an alternative form of evidence, and explain what these astrobiologists base their estimates on instead?
If their alternative evidence is something more a priori, like: "there's a lot of planets and stars out there, there's gotta be some other civilisations," it doesn't seem as compelling as the technosignatures you began with. Also, if they estimate so few alien civilisations per galaxy on whatever non-technosignature evidence or reasoning they have, don't they seem to be assuming complex life is not that substrate flexible? If it were substrate flexible, wouldn't we expect more complex life than about one civilisation per galaxy lifetime?
I apologise if you address this later, or if I've misunderstood something, since I haven't read the whole paper yet! Feel free to ignore this if it's misguided.