Emergentism

One attempt to explain how an immaterial substance like mind could be produced by the purely physical substances that comprise the brain is called emergentism. On this view, when matter of the appropriate types is present in the appropriate complexity and order mind appears much in the same way that "wetness" appears when hydrogen and oxygen molecules combine in the appropriate ratios.

There's nothing inherent in either hydrogen or oxygen that exhibits the property of "wetness," but "wetness" nevertheless emerges from the combination of these two elements, thus wetness is ultimately reducible to material substance. Likewise, materialists argue, mind is not a separate and distinct substance from matter but emerges from it and is ultimately reducible to it.

Neuroscientist Michael Egnor has argued vigorously against this reductionist, materialist view of mind and shares some thoughts on emergentism in this short extract from an interview with Robert Marks at Mind Matters:

Robert Marks: Wouldn’t a materialist ideology require that the mind be an emergent property of the brain?

Michael Egnor: Well, it might even limit us with respect to the idea of emergence. That is, materialism would only be completely consistent with an emergent perspective if the emergent thing was material. That is, if some kind of immaterial soul emerged from brain activity, then that wouldn’t even be a materialist view.

In other words, emergentism is problematic for the materialist because it still allows for the existence of an immaterial soul or mind, however it is produced, which fits very awkwardly in a materialist ontology.

This is a serious problem with emergentism. The H2O molecule is material and wetness is a material property, but this is not analogous to brain and mind. Brains are material but minds are not:

Michael Egnor: [Emergentism] basically doesn’t do any lifting. It’s essentially the invocation of magic. And there are two very serious problems with the concept of emergence in philosophy of mind.

There are emergent properties that are accepted. A classic example is the wetness of water. It’s emergent in the sense that if one studies water rigorously from the standpoint of physics, there’s nothing about it that is particularly wet.

You can study the quantum mechanical attributes of oxygen and hydrogen and all the chemistry and physics of water and not come out of that with anything that suggests that it’s wet. But when you put real water in front of you and dip your finger in it, it’s kind of wet. So people say that wetness is an emergent property of water.

The thing is, with the philosophy of mind, if the mind is an emergent property of the brain, it is ontologically completely different. That is, there are no properties of the mind that have any overlap with the properties of brain. Thought and matter are not similar in any way. Matter has extension in space and mass; thoughts have no extension in space and no mass. Thoughts have emotional states; matter doesn’t have emotional states, just matter.

So it’s not clear that you can get an emergent property when there is no connection whatsoever between that property and the thing it supposedly emerges from.

Egnor adds a second difficulty, which, unfortunately, is less clear:

The other problem with emergence is even more fundamental: When you think about the wetness of water as an emergent property of water, you are really talking about a psychological state. That is, you are saying, psychologically you didn’t expect water to feel wet but by golly, it does. So that’s emergent. But you can’t explain the psychological state [of perceiving wetness] itself as emergent.

He seems to be making the point here that wetness is really the way our senses interpret our experience of water, but the ability to produce the sensation, as well as the sensation itself (like the sensations of color, sound, fragrance, etc.) is not a phenomenon of which matter is capable.

How, after all, do electrochemical processes in the material brain produce the sensation of blue? Where in the brain is the blue? If a microscopically tiny scientist were inserted into the brain and traveled around in it, would he see the brain light up blue, or feel wetness in the brain anywhere?

It's hard to see how matter, acting solely by itself, could create sensations, and it's hard to see how emergentism helps us understand it any better.