In The Phantom of the Opera, Erik uses a strange phrase when speaking to the Persian, saying that oaths are useless:
"Erik," I asked, "Erik, swear that..."
"What?" he retorted. "You know I never keep my oaths. Oaths are made to catch gulls with."
"Tell me... you can tell me, at any rate..."
"Well, the chandelier... the chandelier, Erik?..."
The Phantom of the Opera, chapter XXI: "Interesting and Instructive Vicissitudes of a Persian in the Cellers of the Opera" (translation by Alexander Teixeira de Mattos, 1911)
What does this curious phrase "Oaths are made to catch gulls with" mean? What do oaths have to do with gulls? The only results I can find searching for the phrase have to do with this specific quotation, not found anywhere else.