In 1 Thess.5:23 it uses the words "whole spirit and soul and body". It appears that this supports the trichotomy view of man, because of how it separates the three. However, if my understanding of history is correct, throughout history the Church's official teaching on man is that he is a dichotomy, not a trichotomy.
I also found that the Trichotomy view originated with Plato and then the Gnostics. The Trichotomy view wasn't even considered until the Holiness movement and the Charismatics came around in the late 1800s.

I have read several commentaries on my book shelf on this verse and one coming from a Calvinist Dispi-lite perspective view favors the Trichotomy view.
Other commentaries such as Matthew Henry, did not really state the view it favors.
Another commentary said that every person is a dichotomy, but when they become believers they get the spirit.

Though I favor the dichotomist position, because of the historical position of the Church, I am trying to learn more about the matter, so I can be more dogmatic about the issue. I am also wondering why the verse separates the three.

If anyone can offer help in this, it would be appreciated.

Tom