We recently read JJC Smart's 'Sensations and Brain Processes' in POM. Here, I'll try to explain it to myself. In the article, Smart aims 'to show that there are no philosophical arguments which compel us to be dualists.' He argues for an identity theory of mind wherein:
- there are mental states(/sensations) (MSs) and brain processes(/states) (BPs);
- MSs = BPs;
- and any properties each might have are physical properties (i.e., there are no mental/non-physical properties).
- So there are mental and physical states, but only physical properties.
Wrt the identity part of this identity theory, it's a strict identity between an MS and BP. I think of strict identity as meaning that an identical MS and BP have all their properties in common. What about having parts in common? What might a BP's parts be? Maybe the various physical activities that are part of the experience, e.g., if I stub my toe, some sort of nerve message is sent from my poor toe to my brain which registers pain. I totally made that up, but I hope it's close enough to what really happens in my body when I stub my toe that you get the picture. What might a MS's parts be? Maybe the intensity of the pain. But perhaps he means something else by strict identity. Although he could mean that a part of a BP is identical to a part of an MS.
What this identity does not mean:
- that the MS and BP are temporally and/or spatially continuous
- MS statements may or may not be translatable into BP statements
- the logic of MS and BP statements may or may not be similar
Wrt sensations, they are states of consciousness, or MSs, e.g.,:
- having a yellow-after image
- hearing a bird chirp
- feeling a bee sting on the skin
- having a backache
If I were to say, 'I hear a bird chirping', I'm reporting my MS (or my consciousness or sensation) that I'm hearing a bird chirping, and this MS is a process 'that happens to be' a BP. Physically, at this time my body and brain are doing whatever they do to process audible sounds. Mentally, at this time, I have the sensation that I'm hearing a bird chirping. Bc MSs = BPs, the physical process (my body and brain's shenanigans) is identical to the mental state (my consciousness or sensation of hearing the bird chirp).
This experience of hearing a bird chirp has properties, which might be things like how loud the bird is, the pitch of the chirps, how fast the bird chirps its chirps, where the bird is in location to me, the chirps being muted by a barrier or another noise, etc. But whatever properties this experience has, they are physical properties.
Now, how is it that, bc MSs = BPs, I have a BP that's = a MS, yet any properties associated with the BP and/or MS are physical properties and there are no mental properties to be had?
When I say, 'I hear a bird chirping', that's shorthand for more fully describing the sensation as (paraphrasing Smart here), 'There's something going on which is like what is going on when I have normal hearing abilities, am awake, and there is a bird chirping within hearing distance of me and the chirping is not drowned out by any other sound, that is, when I really hear a bird chirping.' This fuller description notes the similarity between what physically happens when I hear a bird chirping and what mentally happens when (or I have a sensation that) I hear a bird chirping. I may not be able to determine specific points of the similarity between physically hearing a bird chirping and having the sensation of hearing a bird chirping. But I can recognize that the sensation is, on the whole, very much like the physical experience.
Sensations do have properties, but these properties are vague, ambiguous in nature and difficult to identify; or, as Smart puts it, 'colorless'. I'm trying to think what might be a mental property of hearing a bird chirping and I'm not coming up with much besides the overall auditory experience, an image of a bird chirping away in a tree, etc., i.e., I'm not coming up with identifiable individual mental properties. But that could be due to a lack of imagination on my part.
Just bc we have difficulty picking out a sensation's properties doesn't mean that they must be mental/non-physical properties. We can identify the physical properties of a BP. And we recognize the similarity between a BP's properties and a sensation's properties. This similarity is enough to say:
- yes, sensations have properties;
- it's hard to pick them out/identify them;
- so we don't really know what they're like;
- since we don't really know what they're like we can't say that they're mental/non-physical in nature;
- but we do know that they're similar to identifiable physical properties;
- so, instead of positing that sensations have mental properties, let's posit that sensations have physical properties.
Smart deals with some objections, most notably one which suggests that, even if MS = BP, there must be some properties other than and distinct from physical properties. I'll go over that objection and his response when I sum up Jerome Shaffer's 'Mental Events and the Brain', which suggests something very similar. For now:
Shorter Smart: MSs and BPs are identical (i.e., MSs are physical processes). MSs and BPs have only physical properties. So, there is no need to posit any irreducibly mental properties to MSs or BPs. It's all physical, so no need to be a dualist.