The trick is most obvious in short passages like this:
- "Not that I loved Caesar less, but that I loved Rome more." (Julius Caesar, III, ii)
- "Beautiful tyrant! fiend angelical! Dove-feather'd raven! wolvish-ravening lamb!" (Romeo and Juliet, III, ii)
- "To be, or not to be -- that is the question." (Hamlet, III, i)
Now, the Rhetoric Cops will tell you that antithesis is the "juxtaposition or contrast of ideas or words in a balanced or parallel construction." That describes the individual lines I just shared with you, which show antithesis on the small scale. What is also true, and important, is that this trick works on the very large scale. (By the way, I just used the trick there -- did you notice it?)
One of the really jaw-dropping moments for any writer who also happens to be a Shakespeare freak comes when it becomes apparent that this seemingly simple trick of playing with opposites is driving extremely complex structural and thematic decisions.
An early example is ROMEO AND JULIET: two houses set in opposition, two sets of parents, two lovers, etc. A later, and much more rich, example is ANTONY AND CLEOPATRA: Rome embodies a thematic "world" that stands in opposition to the "world" set out in Egypt by Cleopatra, and Antony must choose between the two.
One realizes fairly quickly that this "opposites game" is something close to an obsession with Shakespeare, one that becomes more important as a tool as his career progresses.
For my part, I believe this fixation on opposites is the engine behind what the critics call "negative capability" in Shakespeare's plays. (Academic doubletalk alert!) "Negative capability" just means Shakespeare's ability to get an audience to see a person, an issue, or question from multiple angles. If there is a writer who does this better than Shakespeare, I don't know who it is. And I feel quite certain that antithesis (as well as its cousin, oxymoron) are a big part of how he pulls it off on both the small and the large scale.
Antithesis is one of those writerly tricks (like personification) whose frequency you may not notice in Shakespeare until it's pointed out to you. Once you spot it, though, you are likely to see examples of antithesis in many, many places in Shakespeare. Soon, you won't be able to stop looking for them.
Now it's your fixation. Will obsessing about how you can use antithesis become a form of lunacy -- or will mastering this trick prove to be the sanest thing you've ever done as a writer?
Have fun.