The Interaction Problem

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

In today's post I'd like to highlight one of the common objections materialists make to the belief that we are at least partly comprised of an immaterial mental substance.

This is the objection based on what's called the interaction problem. The problem is that it's inconceivable or unthinkable that two completely different substances, mind and matter (or brains), 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 somehow they 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 them. That is, material entities - the brain 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:

• The idea of food, an immaterial phenomenon, 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 assume a priori that materialism is true, but the truth of materialism is the very point that's in question in this discussion. To assume that materialism is true at the outset and then conclude that indeed it must be true is to commit the logical fallacy known as begging the question.