Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

A man approaches a faith healer, begging to be cured of his "horrible gullibility." The preacher obliges, shouting "Hear me, demons of gullibility! I cast you out!" The man immediately feels cured and declares "My God... I see so clearly now!" -- but then notices the preacher is wearing an earpiece. The preacher claims it is a hearing aid, but the man is suspicious: "If you're a healer, why would you need it?"

The man's briefly-cured gullibility kicks in and he realizes it is actually a tiny radio used to receive information from the show's producers on the sly -- which is how the preacher knew his name before being told. Just as the man declares "I'm no longer gullib--" the preacher interrupts: "Don't worry, it's the placebo effect. In three seconds it'll wear off and you'll be normal again." The man immediately reverts, shouting "Praise the Lord!"

This is a bonus comic created to promote the book "Soonish" by Zach and Kelly Weinersmith.

The Humor

The joke is a beautifully constructed paradox. If the faith healer actually cures the man's gullibility, the man will see through the faith healer's act -- making the cure self-defeating for the healer. When the man does briefly become skeptical, he correctly identifies the earpiece scam (a real technique used by fraudulent faith healers like Peter Popoff). But the healer simply tells him the cure was a placebo that will wear off, and the man is gullible enough to believe this, instantly reverting. The circular logic is the point: gullibility is its own trap, because the very credulity that makes someone seek a faith healer also prevents them from recognizing the fraud.

References

The earpiece detail is likely a reference to televangelist Peter Popoff, who was famously exposed in 1986 by James Randi for using a radio earpiece through which his wife fed him information about audience members, making it appear he had divine knowledge.