Juxtaposition places two or more dissimilar characters, themes, concepts, etc. side by side, and the profound contrast highlights their differences. Why is juxtaposition such an effective literary device? Well, because sometimes the best way for us to understand something is by understanding what it’s not.
Example: In the opening lines of A Tale of Two Cities, Charles Dickens uses juxtaposition to emphasize the societal disparity that led to the French Revolution: “It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness…”
Similar terms: oxymoron, paradox