What is the theory behind (if any) in architectural design using round column or

Question:

What is the theory behind (if any) in architectural design using round column or square column?

I'm in the middle of learning up some architectural concept and theory. Wish to know more in of the theory behind some architectural design on Column, when do we use round column, or when do we use square column for a building design, are there any theory behind by using round column instead of square column in architectural design?

Best Answer - Chosen by Asker:

I'm an art historian not an archeitect and my focus wasn't architectuire so take this with a grain of salt; but the main difference between columns and piers (square columns) is the asthetics of the archietect or the culture involved.