A character, sir, may always ask a man who he is. Because a character has really a life of his own, marked with his especial characteristics; for which reason he is always "somebody." But a man—I'm not speaking of you now—may very well be "nobody."
The Father makes this playful comment to the Manager in Act II. Note the mellifluous courtesy of his speech: this rhetorical ploy is typical of the speech he addresses to the company or at his moments of relative reserve. Throughout the play, the Father insists on the reality of the Characters, a reality that, as the stage notes indicates, inheres in their forms and expressions. Here he bristles at the Actors' use of the word illusion as it relies on its vulgar opposition to reality. He approaches the Manager in a sort of face-off to challenge this opposition, one that underpins his identity. Convinced of his self-identity, the Manager readily responds that he is himself. The Father believes otherwise. While the Character's reality is real, the Actors' reality is not real. While the Character is somebody, man is nobody. Man is nobody because he is subject to time: his reality is fleeting and always ready to reveal itself as illusion, whereas the Character's reality remains fixed for eternity as art—what the Actors would call mere illusion. Put otherwise, time enables an opposition between reality and illusion for man. Over time, man comes to identify realities as illusion, whereas the Character exists in the timeless reality of art.