Who decides to what degree a build...

Who decides to what degree a building gets designed and built? The architect? The owner? The contractor?
There are those who declare the proprietor to be all-powerful. After all, who's paying the bill?
Others believe that no other than the architect can be considered the actual soul of any building, for without a design, in what manner could there be a form in the first place?
Still others side with the contractor, who must transform the architect's vision into a physical entity, while keeping the work at jobs on time and within stock for the owner.
The answer to the conundrum of in what manner buildings really ...