I recently read Thomas Nagel’s mercifully short Mind and Cosmos — mostly just to see what all the fuss was about — and one of the weirder lines of enquiry he pursues concerns what he calls the ‘historical problem of consciousness’. This is the problem of how consciousness came to be, which Nagel wants to distinguish from the ‘constitutive problem of consciousness’, i.e. the problem of what consciousness is. He writes [1]:
The historical account of how conscious organisms arose in the universe can take one of three forms: it will either be causal (appealing only to law-governed efficient causation), or teleological, or intentional.
A causal explanation is the sort of thing a Darwinian account of the evolution of consciousness might offer, while an intentional explanation would appeal to the plans of some agent who made things happen the way they have (guess who). Teleological explanation is murkier, and it is here that Nagel positions himself, attempting to stake out some sort of middle ground between theism and materialism.
Teleological explanations of a sort do appear in science — particularly in biology — but usually with the proviso that they are to be understood as shorthands (or sometimes heuristics) for lower-level causal explanations. So we might explain the web-building behaviour of spiders in terms of its purpose (i.e. spiders build webs in order to catch flies), but on the understanding that the ‘purpose’ of an organism’s behaviour just refers to those of its causal effects which increase the organism’s inclusive fitness.
Even intentions crop up: when a gene has effects which result in its spread through a population (altruistic behaviour in cases of kin selection is a favourite example) it can be helpful to think of the gene as an agent with goals. But this kind of agenthood is underpinned by the fact that genes have causal effects which can influence their own spread, and so can be regarded as beneficiaries of these effects. Genes are agents, then, only insofar as their interactions can be modelled using game theory, and this is a criterion which can be cashed out in purely causal terms.
It can also be tempting to ascribe teleological features to systems which have intrinsic tendencies. So we might say that soap bubbles ‘want’ to become spheres, or (more generally) that dynamic systems ‘want’ to minimise their free energy. But here, as in the above cases, this can be understood in terms of patterns of efficient causality at lower levels which give rise to emergent features at higher ones. (Rather than the spread of traits through populations, in this case the causal explanation might mention singularities in a system’s phase space, for example.)
None of this is quite what Nagel is after. He wants some form of teleology which neither can be paraphrased away using efficient causes, nor which requires a real agent. This jams him into a rather narrow crease, and forces him to say things like “Each of our lives is a part of the lengthy process of the universe gradually waking up and becoming aware of itself” while unable to say anything substantial about what it means for the universe to be the sort of unity which can ‘wake up’. The faint whiff of woo that rises from such statements no doubt accounts for much of the scorn that has been poured on this book since it was published in 2012.
And perhaps not all of it fairly — while Nagel is not quite sure what exactly he is proposing (he admits as much, so props to him) he does have some idea what the presence of ‘natural teleology’ would imply, and that may be enough [2]:
Natural teleology would require […] that the nonteleological and timeless laws of physics […] are not fully deterministic. Given the physical state of the universe at any moment, the laws of physics would have to leave open a range of alternative successor states, presumably with a probability distribution over them.
And then [3]:
The existence of teleology requires that [those] successor states [which lead to the formation of more complex systems, and ultimately life] have a significantly higher probability than is entailed by the laws of physics alone […] Teleological laws would assign higher probability to steps on paths in state space that have a higher “velocity” toward certain outcomes.
These implications offer a way of empirically testing for natural teleology in indeterministic transitions. If, say, indeterministic quantum effects played a critical role in gene mutation, and we suspected that this is somewhere that natural teleology might manifest, we could gather measurements of these events and see whether the spread of our results deviated from the expected probability distribution given by quantum mechanical laws. Being a wise sort of chap Nagel never mentions quantum mechanics, but we can see how this kind of test might work even if natural teleology was hypothesised to operate at some as-yet-undiscovered lower indeterministic level.
If quantum indeterminism is supposed to be a site of teleological influence, then we could be forgiven for wondering why Nagel isn’t out there doing experiments to look for it. But if it isn’t, then Nagel’s claim puts strong constraints on the shape of future physics. All this just serves to highlight something that should already be clear: Nagel’s thesis is highly speculative, and whether or not it should be given serious consideration depends entirely on the hopelessness of alternatives. The subtitle of Mind and Cosmos is the snappy “Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False”, so this is not a question he leaves unaddressed. But personally I found it all a bit toothless (I think a more accurate subtitle would have been “Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly Inconsistent with a Wagonload of Dubious Claims about Cognition and Moral Ontology, Surprise Surprise”). Here, however, is not the place to get into it — if you’ve read the book (or have just been following the fallout) and have some thoughts, please do drop in with a comment.
Notes:
1. Chapter 3, Consciousness.
2. Chapter 4, Cognition.
3. ibid.
The Platopus 