Themes
The work above its performance
Wilde holds that 'the stage is to a play no more than a picture-frame is to a painting'. His proof is that the two great English plays of the century, the Cenci and Atalanta in Calydon, cannot be acted, and that London and Oxford productions of Browning tested only the stage, not the plays. The letter's sharpest line turns this into a rule: 'It is not, Sir, by the mimes that the muses are to be judged.'
The danger of personality
Wilde's objection to actors is their personality, which 'may distort' and 'may be a discord in the tone or symphony.' Puppets, by contrast, 'have no personalities at all', recognise 'the presiding intellect of the dramatist' and never do good in public or save people from drowning. The joke carries a real claim about acting: the actor should convert his 'accidental personality' into the character's, and Wilde notes two schools, exaggeration and suppression, without choosing between them.
The artist's independence
The closing defence of John Gray becomes a statement of how an artist should stand towards the world. Protection no longer comes 'in Prince, or Pope, or Patron', but in 'high indifference of temper', the pleasure of making beautiful things and a sense of humour that sees 'how vain and foolish is all popular opinion'. The same scorn runs through the rebuke to the journalist, whose report is a jade 'who lies without lovely invention'.