Causation and dualism

Traditionally, many Christians subscribe to substance dualism. That is to say, they think humans have an immortal, incorporeal soul. That's largely based on Biblical passages which indicate an intermediate state between death and the general resurrection. That when you die, you don't cease to exist. Consciousness survives brain death. And I think that's correct. 

A stock objection to dualism is that it's hard to see how one kind of substance (matter) can act on another kind of substance (mind) or vice versa. 

This is based almost entirely on the intuition that causation involves a point of contact. It can be direct contact between cause and effect, or it can be energy transfer that's transmitted through an intervening medium. A physical chain of cause and effect–like a game of pool or dominoes.  

Let's consider some comparisons. Alcohol is a mood-altering chemical. At least in theory, it's not hard to grasp how ingesting or imbibing a chemical substance can affect brain chemistry. Beer and brain are both physical substances.

Compare that to a hug. Hugs are mood altering gestures. But it's harder to explain how gentle, momentary pressure on the sternum can affect one's mood.

The stock explanation is appeal to oxytocin. A hug releases oxytocin, which has a chemical effect on the brain. 

And that may be true to some degree. However, to explain the effect of a hug by reference to oxytocin only pushes the question back a step, for you must then explain how a neuropeptide have that effect. Is a neuropeptide really responsible for all the varied dispositions that people attribute to it? For many people, a hug is deeply meaningful in a way that seems to be irreducible to stimulating one neuropeptide. 

It seems more plausible to explain the mood-altering effect of a hug as innate code language. We've been designed to interpret a hug as a social signal. 

In any case, the effect seems to be further removed from the physical cause in that instance than alcohol consumption. 

Be that as it may, let's consider one further example, which is even more detached from a point of contact: watching a movie or a game can be a mood-altering experience. It can make the viewer happy, sad, or mad. It can be exciting. 

What the viewer sees causes a mood in the viewer. But what is the nature of the cause? It doesn't act on the brain in any direct sense. 

Rather, certain images hold personal significance for the viewer. In a movie, he may relate to some characters. He cares about them. He becomes invested in what happens to them.

He can related to their situation. So he is drawn into the story, as if it was happening to him. 

It has an emotional effect on him, but that's a purely intellectual, interpretive exercise. Things we see can affect our mental states, not because there's a point of physical contact, but because they are significant to the viewer. That's a cause/effect relation between two disparate substances.