Rick, you really can't have a theory as such, there has been for a long time and is in all of my aero books one big hairy set of aerodynamic force and moment equations that determine what an airplane will do.

An airplane can go up if the numerical solution of the set of equations gives a velocity in the up direction.

An airplane can go down if the numerical solution of the set of equations gives a velocity in the down direction.

An airplane can slow down ...................... you get the picture.

It means that you can give up elevator and go up or down depending on other factors. Throttle can make you go up or down, flaps can make you go up or down ................. another "you get the picture".

The fact that there are several combinations of power, control surface deflections, weights, wing area, configurations that make the answers vary is what makes aero an interesting area.