Disclaimer: This is a follow up to my previous posts on the philosophy of mind series with Marianne Talbot. I suggest that you read those first to familiarise yourself with the arguments and terminology referenced in this post.
Physicalist theories of mind, such as anomalous monism and functionalism, become problematic when considering certain features of mental things that are (at least in the absence of argument) generally held as true. Mental things seem to cause physical things (I have a desire to open the door so I put my key to the lock); and they also seem to have a specific quality of what it is like to be that thing (what it is like to be in pain, or to feel angry, or to see blue). Epiphenomenalism and eliminativism are two alternative theories of mind that attempt to overcome these problems; either by denying that mental things cause other things, or by denying that mental things really exist.
The epiphenomenalist believes that mental things exist, and that they are caused by physical things. In the same way that the light bulb inside my lamp generates light from electricity, mental things – feelings, colours, beliefs and so on – are generated from neural activity in the brain. In this way, when I put my key to the lock to open the door, my action is caused by a physical thing (presumably a specific pattern of neural activity n that causes my action a).
Moreover, it is possible that the same neural activity n can cause both my desire to open the door, and my action towards opening it. In other words, two things can share the same single common cause. The electricity going in to the light bulb can cause light and my experience of it; so neural state n can cause my desire to open the door and my action towards it. Because of this, the epiphenomenalist avoids the problem faced by the anomalous monist, who tries to attenuate the problem of mental causality by giving mental things a physical description – but in doing so makes mental things causally redundant.
But if mental things cannot cause physical things, then we must also claim that our feelings and beliefs don’t cause us to act in one way or another. Do I not turn up to work because I feel some obligation to be there, and because I believe that if I do not turn up I will be fired? The epiphenomenalist thinks that it is not these mental things that cause me to turn up to work – but the corresponding (physical) neural states. An argument against the epiphenomenalist’s claim would therefore have to show that a causal relation between the mental thing (a belief, for instance), and the physical thing (showing up to work) can be caused by something other than neural state x. This is possible in principle (neuroscience might discover that my belief and the corresponding action can be caused by multiple neural states), but even if this were true, it would still be true that mental things (and their corresponding actions) are caused by physical things.
It is worth clarifying what the eliminativist means when they say that mental things don’t really exist. For the eliminativist, mental things – beliefs, desires, the colour blue – are useful ways of describing what happens when we behave in certain ways. For example, it is useful to describe my going to the freezer to get ice-cream in terms of my like of and desire for ice-cream. But these terms ‘likes’ ‘desires’ don’t capture anything real – i.e. there doesn’t really exist something that is a like or a desire – they are simply theoretical terms used to describe behaviour. What is really happening when I go to the freezer to get ice-cream is that neural state a interacts with neural state b in such a way as to cause my actions.
In principle, it is possible that neuroscience will discover every reason for our doing whatever action it is that we do; at which point our use of likes and desires to describe our reasons for acting will become scientifically redundant. If what the eliminativist argues is true, then what it is like to be something – to be in pain, to feel angry, to see blue – is not a thing in its own right, but a by-product of our underlying neural activity. This is a bold claim, for it means that what we take to be beliefs, feelings, colours etc, are merely illusory: there are simply reasons for why things are the way that they are and behave in the ways that they do. For this reason, even Descartes cogito – ‘I think, therefore I am’ – is rendered invalid: if there is no such thing as a thought, then what it is to be is something other than the existence of thought. A valid rendering of the cogito under the eliminativist would use a causal reason to explain self-consciousness; in the same way that we increasingly use causal reasons to explain the behaviour of animals and other natural phenomena.
It is worth noting that if what the eliminativist argues is true, then it is possible that a computer could be programmed to behave in exactly the same way that we do, and, moreover, that this computer would be indistinguishable to a human being in every way except its genesis (and if the simulation argument is to be believed, then even this truth is open to doubt).