Apostrophe breaks off from the audience to address someone or something absent — a dead person, an abstraction, an object, an enemy who is not in the room. The real audience listens in, and the fact that they are overhearing is the point.
Nothing can be settled by addressing an abstraction. What the figure provides is intensity.
Donne opens a sonnet by addressing mortality directly: “Death, be not proud, though some have called thee / Mighty and dreadful, for thou art not so.” Death does not answer. The argument is for the reader, conducted over Death's head.
Not to be confused with the punctuation mark of the same name. The rhetorical figure and the mark share an etymology and nothing else.
Apostrophe raises the temperature of a passage by changing who is being spoken to, and the audience experiences the shift as an escalation even though no new information has arrived. This is its entire mechanism, and it is why the device belongs to poetry and oratory rather than to analysis.
In argument it has one legitimate use and one common misuse. The legitimate one is to make an abstraction concrete enough to reason about — addressing a principle directly can clarify what following it would actually require.
The misuse is substitution. A writer who cannot answer an opponent may instead address the absent opponent passionately, and a reader carried along by the vehemence may not notice that the reply was performed rather than made. The figure is safe when it sits beside an argument and unsafe when it stands in for one.
