stark raving sane

R: "Ah, I think I've got it. A man talking sense to himself is no madder than a man talking nonsense, not to himself."

G: "Or just as mad."

R: "Or just as mad."

G: "And he does both."

R: "So there you have it."

G: "Stark raving sane."

• Rosencrantz and Guildenstern are Dead, Tom Stoppard