As an actor you need skin as thin as glass in front of the camera and the opposite in the movie business where it has to be thick as hide. 

Can help you see what is the thing and what it isn’t.

Asking the question allows you to give an answer which in turn allows you to think of the opposite answer.

Opposites can unearth your imagination.

When writers ask the question ‘What if?’ that can provoke the opposite.  

Raising the opposite can be useful at the beginning of your work when assumptions might be made that haven’t taken enough into consideration.

What is the opposite challenges you to defend your position.

Story is filled with opposites. As is life. Young and old; birth and death; love and hate; good and evil; rich and poor; female and male; language, nationality, religion, etc.

When we say drama has conflict opposition is inherent in the conflict.

Aristotle, in his Poetics, defines peripeteia as "a change by which the action veers round to its opposite, subject always to our rule of probability or necessity."