I have virtually zero experience in Pathfinder, so I may very well be missing a ruling in the corebook on this.
The warrior with a far reaching spear in tandem with the shield is a tried and true historical one. I'd like to make one for the game. Can it be done? My hope was to give him a shield to bash adjacent foes and the spear for the further ones. However, I don't see any rule on using a reach weapon with one hand. This is a weird case of real physics being more permissible than game physics.
Is there a way to build this concept, even if it takes a few levels to get it there?