The success of natural science over the last five hundred years has been truly mind-blowing. It doesn’t follow, however, that science is well-suited to answering all questions. Sam Harris has suggested that science can answer the questions of ethics as well as our questions about the nature of reality. But like many, it seems to me that there are many ethical questions which are just not suited to being answered scientifically. There’s no experiment that will tell us whether ethics is ultimately about maximizing good consequences or about fundamental rights and duties.
It is commonly assumed that the task of explaining consciousness is scientific rather than philosophical. I think that’s half right. It’s the job of neuroscience (among other things) to establish the neural correlates of consciousness (NCCs), that is, to work out which physical states of the brain are correlated with which subjective experiences. We have a robust and well-developed experimental approach for answering these questions.
However, establishing the NCC is just one half of a theory of consciousness. We also want to explain those correlation, to work out why certain physical states are correlated with experiences. As things stand, I think this is a philosophical rather than a scientific question. Philosophers have offered a number of different answers to this question. Here are three of them:
- Naturalistic dualism – A subjective experience is a very different kind of thing from a physical brain state, but the two are bound together by natural law. In addition to the laws of physics, there are fundamental psycho-physical laws of nature which ensure that, in certain physical circumstances, certain experiences emerge.
- Materialism – Each subjective experience has a purely physical nature. Having subjective experiences – feeling pain, seeing red – wholly consists in having certain complex patterns of neuronal firing.
- Panpsychism – Each physical state has a purely experiential nature. Physical science tells us what matter does whilst leaving us in the dark about what it is. Having physical states – being negatively charged, being a certain pattern of neural firing – wholly consists in having certain kinds of subjective experience.
All of these theories are empirically equivalent: there is no experiment that can decide between them. That’s not really a surprise, as this is not a purely empirical question. It’s rather a question of why something that is publicly observable (brain activity) always goes together with something that is not publicly observable (subjective experience). This is isn’t the kind of question an experiment can answer, just as questions about the fundamental character of ethics can’t be answered experimentally.
One option is agnosticism. If we can’t decide between these views experimentally, then maybe we should simply say that we don’t know which is true. Another option is to try to decide between them on the basis of non-experimental considerations. In other words, to do philosophy.
If I don’t think explaining the NCC is a scientific question, why is my book subtitled ‘Foundations for a New Science of Consciousness’? The task of explaining the NCC is currently in the domain of philosophy. But when a broad consensus arises as to how to address a question, philosophy turns in to science. The aim of my book is precisely to develop such a methodology for that bit of the science of consciousness which is currently in the domain of philosophy.
So is it the job of science or philosophy to explain consciousness? As things stand, the task of accounting for consciousness is partly scientific (establishing NCCs) and partly philosophical (explaining the NCCs). If we one day achieve societal consensus on how to address the latter half of the puzzle, the task of accounting for consciousness will move entirely into the domain of science. I think this is starting to happen, but – just as at the start of the scientific revolution – there needs to be some serious engagement with philosophy before we get there.