Final answer:
The quote by F. Scott Fitzgerald about holding two contradictory ideas shows that concepts in opposition can coexist in a first-rate mind.
Step-by-step explanation:
The line that shows that ideas usually in opposition can be the same is found in the famous quote by F. Scott Fitzgerald: "The true test of a first-rate mind is the ability to hold two contradictory ideas at the same time." This statement encapsulates the concept of cognitive dissonance where a person can understand and accept two conflicting concepts simultaneously. Fitzgerald uses this idea to challenge readers to recognize the complexity within human thoughts and opinions. It suggests that a nuanced understanding and the ability to resolve contradictions are marks of advanced thinking and intellect, which is especially important in disciplines like microeconomics, where multiple contradictory ideas often need to be considered in tandem when studying markets and government interrelationships.