The Interaction Problem

I've run a few posts on the topic of mind and matter this past week, largely because we've been discussing it in my classes, and because the topic is, I think, fascinating.

There's one more thing I'd like to say about it, particularly with regard to one of the common objections materialists make to the belief that we are at least partly comprised of immaterial mental substance. This is the objection based on what philosophers call the interaction problem. The problem is that it's inconceivable or literally unthinkable that two completely different substances, mind and matter (brain), could in any way interact with each other. Given that we can't describe how brains interact with immaterial minds and vice versa, belief that they somehow do is unwarranted, or so it is claimed.

The problem with the interaction objection is that it seems to be based on the assumption that something can only be affected by other things which are like it. That is, matter, like brains or bodies, can only be affected by other things which are material, but this principle - that like can only affect like - is surely not true. We see counter examples all around us:

• An immaterial phenomenon like the idea of food causes the physical reaction of salivary glands secreting saliva.
• The excitation of cone cells in the retina, a physical reaction, produces the sensation of red which is non-physical.
• Swirling fluid in your inner ear, a physical condition, causes the sensation of dizziness which is non-physical.
• Getting your fingers caught in a closing car door, a material situation, causes pain which is an immaterial phenomenon.

And so on. The only way that the principle that "like causes like" can be known to be true is if we know to start with that materialism is true, but the truth of materialism is the very point that's in question in this discussion.

The materialist can attempt to evade the examples given above by insisting that ideas, color, pain and other sensations are not really immaterial phenomena but are merely names we give to certain types of neurochemical events in the brain, but this is unconvincing. It may be that when you experience pain there are certain chemical reactions occurring in your brain and certain nerve fibers being stimulated, but those physical phenomena are not what pain is any more than thunder is the same thing as lightning. In fact, thunder can at least be explained in terms of lightning, but there's no way to explain how nerve fibers firing produces pain.