According to Patricia Churchland, neurophilosophy studies “the impact of discoveries in neuroscience on a range of traditional philosophical questions about the nature of the mind”. The term has been around for more than three decades, but it doesn’t seem to have really caught on – apart from Churchland and her husband Paul, there aren’t too many philosophers who use it, let alone label themselves as “neurophilosophers”.
Why is that? I think it might have to do with the fact that the term, as used by Churchland, is ambiguous, and when we clearly distinguish between its two meanings, it’ll turn out that in both cases it can be quite misleading. There is neurophilosophy in a broad sense, which is what Churchland explicitly says it is: appealing to neuroscience to make philosophical claims about the mind. But there is also a narrow sense, which she uses more often: appealing to neuroscience to make philosophical claims about the mind that Churchland agrees with.
What are those claims? First of all, Churchland believes that findings from neuroscience support physicalism – the view that all that exists is physical stuff that physicists talk about – and undermines dualism – the view that in addition to the physical stuff there is also some non-physical stuff, like subjective conscious experience. She lists a number of findings that she thinks “weigh in favor of the hypothesis that mental functions are a subset of functions of the physical brain, not of some spooky ‘soul stuff’”. For example, she argues that what we know about the evolution of the homo sapiens brain clashes with traditional religious views which assume that only members of the homo sapiens species have immortal souls. Or she argues that what we can learn from the research on split brain patients speaks against the religious view about the unity of the soul.
However there are also religious philosophers – like, say, Peter van Inwagen – who argue that their views are not undermined by findings mentioned by Churchland. Yes, I think their arguments are terrible, but this is beside the point. The fact remains that they also appeal to neuroscience to make philosophical claims about the mind – that is, they engage in neurophilosophy in the broad sense.
Moreover, there are also dualists like David Chalmers who don’t believe in immortal souls or any kind of “spooky soul stuff” that does physical stuff. Churchland thinks they’re wrong too, and her argument boils down to the point that they’re unable to explain how the physical is supposed to interact with the non-physical. On the other hand, Chalmers argues physicalists face a much more serious problem trying to explain consciousness in purely physical terms. Regardless of who’s right about this, both discuss what kind of impact neuroscience can have on philosophy of mind.
Churchland believes that neuroscience points to physicalism, but not to any kind of physicalism. There are physicalists she deeply disagrees with, most prominently those who subscribe to some form of functionalism. The basic idea is roughly this: just like the same software can be run on many different types of hardware, the same mental state can be realised by many different neural – and possibly non-neural – structures. And just like understanding software is not about understanding a particular piece of hardware it can be run on, understanding mental states is not about understanding possible neural – or non-neural – mechanisms behind them. Rather, it’s about understanding how they interact with other mental states, stimuli and behaviour. Phenomena like beliefs, desires, memories, hopes etc. can only be adequately explained in terms of the role they play in this kind of system.
Churchland says that recent discoveries in the neuroscience of decision-making, attention and spacial representation show that psychology is not detached from neuroscience in the way that functionalists would like it to be. But functionalists seem likely to reply either by saying that those results don’t actually threaten functionalism, properly understood, or that even if they do undermine functionalism in some way, they hardly constitute a death blow to it – we’re still miles from knowing whether the functional analysis of mental states is a viable project, or whether it only makes sense to explain them (or explain them away) in neural terms. In any case, again both Churchland and her opponents argue that neuroscience is related to philosophy of mind in some way – they just disagree about what this relation is.
To sum up: neurophilosophy in the broad sense is something that pretty much all philosophers of mind engage in – it’s just hard to do philosophy of mind without specifying one’s view about its connection to the science of the brain. However calling every instance of discussing this connection “neurophilosophy” doesn’t seem very helpful, as it suggests we’re dealing with some separate philosophical discipline in its own right rather than with a certain type of evidence, or a certain class of arguments within a philosophical discipline, namely philosophy of mind. It’s just as misleading as trying to call any kind of appeal to, say, economics in philosophy “econophilosophy”. On the other hand, neurophilosophy in the narrow sense amounts to being Churchland’s view about the relation between neuroscience and philosophy of mind. In this case the term is misleading as it suggests her view is somehow more “neuro” than other views.
Here Churchland might object that the difference between what she does and what dualists or functionalists do is that she pays way more attention to the results of neuroscientific studies and discusses them in detail. This may be true, however in many cases I’m not sure whether she actually needs to get into all that detail to make her point. For example, let’s ask: what kind of neuroscience results would count as evidence for, say, Chalmers’s property dualism, according to Churchland? The answer seems to be: there are no such possible results. This suggests that Churchland doesn’t really rely on data she often cites as far as her philosophical arguments are concerned. Which I think would be more obvious if her work didn’t have the “neurophilosophy” label stuck on it.
* I suspect that Churchland’s tendency to include lots of what seems to be philosophically irrelevant (by her own standards) neuroscientific data has to do with her misreading of Quine and her mistaken views about the role of conceptual analysis in philosophy, but that’s a topic for another discussion.