Thought 9: Are people made up of one part, two parts, or three parts?

I was lead to believe (or taught to believe) that people are made up of three parts.  Body, soul, and spirit.  The soul and spirit were all mushed up but clearly kept separate from the body.  Any changes to my body didn't effect my identity.  I am an animating force driving my body around like a vehicle.  When I die I will dispose of my body and get a new one, much like selling an old car and getting a new one.

The problem with this view of reality is that it overlooks certain key facts.  My brain has a very real impact on how I act.  Head injuries can change my personality.  This isn't a debatable topic.  There have been enough studies done on patients with head trauma and enough research done into what each part of the brain does that this is settled science.

So, who am I?  Is my personality controlled entirely by my brain?  If so then that would lead me to think that I am a deterministic machine.  Every choice I make is the consequence of a series of chemical interactions and my brain plotting out how to solve problems.  Perhaps there is a little tiny random number generator in there somewhere when I have to make a choice.

There is evidence that the brain isn't even entirely in control.  If you smile a lot you will feel happier.  If you exert your will (which is what again?) to frown a lot you will feel worse.

Before we go too far down the rabbit hole science still doesn't know what produces self awareness.  We understand a little bit about how the brain works but we don't understand how cognition works.  We can perform a task and watch which part of the brain lights up to see how it is segmented but we don't know why it works the way it does.

So, am I one, two, or three parts?  If I am multiple parts how do they interact?  Does my body act less like a vehicle and more like a filter?  Every stimuli and experience that my soul or spirit or soul/spirit combination would receive has to be brought to it via my body somehow.  How does that lead to a situation where my brain being injured changes my soul/spirit personality?  Is this proof that a person isn't broken up into constituent parts that interact like objects in an OO computer program?

Yet we have parts of the Bible that talk about us having a new body.  Paul talks about leaving this body for a new one like taking off clothes to put on new ones.  The more science digs in the more it looks like who we are as people is tied up in our bodies.  I do believe there is something more to us than just chemical processes, but I think the model view of a soul piloting around a body is wrong as well.

If you cut off my arm it doesn't change who I am in my identity, but it will change my life.

I do think we're at least 2 parts, body and soul.  I imagine an argument could be made for 3 parts, but I have no reason to believe that over  2 parts.  I guess for now I'll just assume we're 2.5 parts.