This line from Charles Dickens’s A Tale of Two Cities exemplifies an antithesis.
In the second part of this line, the author is setting exactly the opposite stated in the first one.
Antithesis means "setting the opposite." Antithesis is implemented in writing or speech either as a proposition that contrasts with or reverses a previously mentioned proposition, or when two opposites are introduced together in order to create contrast.
Antithesis can be defined as "a figure of speech entailing a seeming contradiction of ideas, words, clauses, or sentences within a balanced grammatical structure. Parallelism of expression serves to emphasize opposition of ideas"