The process of having two people or groups play opposing roles in a debate to better understand a proposal is known as the method.

Dialectric Method

Explanation:

This method is one in which two or more persons having different opinion or systematic resoning about a subject matter aims at driving their point with the objective of disputing the other persons argument. It is basically a means of comparing facts via logical argument.

The north used the rising number of immigrants to staff the industrial economy (factory jobs, warehouse jobs, etc...) the south felt no need to employ immigrants on their plantations because the invention of the cotton mill had made slavery a more economical option.