1. Antithesis
A rhetorical device

5. Antithesis defined
a figure of speech which contrasts ideas, words and concepts in one sentence. However, contrasting words like bittersweet, Icy Hot, jumbo shrimp etc. aren't antithesis. They are examples of oxymoron. To be an antithesis, a sentence should have contradicting words positioned in a balanced way in a phrase or a clause. 

6. Why?
uses words to convey ideas in different ways from the common words and expressions of daily life. Thus, it conveys meaning more vividly than ordinary speech. When contrasting ideas are brought together, the idea is expressed more emphatically.
As a literary device, antithesis makes contrasts in order to examine pros and cons of a subject under discussion and helps to bring forth judgment on that particular subject.

7. Much Ado example:
BEATRICE: …He that hath a beard is more than a youth; and he that hath no beard is less than a man: and he that is more than a youth is not for me; and he that is less than a man, I am not for him: therefore I will even take sixpence in earnest of the bear-ward, and lead his apes into hell.
(II, i, 36-41)

8. Note the syntax!
BEATRICE: …He that hath a beard is more than a youth; and he that hath no beard is less than a man: and he that is more than a youth is not for me; and he that is less than a man, I am not for him: therefore I will even take sixpence in earnest of the bear-ward, and lead his apes into hell.
(II, i, 36-41)
Semicolon – provides a more emphatic separation than a comma and affords an easier transition between independent clauses than a period. Thus, it is the most appropriate punctuation to balance two contrasted ideas in parallel form.

9. Note the syntax!
BEATRICE: …He that hath a beard is more than a youth; and he that hath no beard is less than a man: and he that is more than a youth is not for me; and he that is less than a man, I am not for him: therefore I will even take sixpence in earnest of the bear-ward, and lead his apes into hell.
(II, i, 36-41)
Colon – used to introduce the effect or logical consequence of an action.