"The doctors were all wrong, and/or everything they did was useless!" cry the believers. "God brought him back, its god that is in control!"
And watch them scurry to the doctor's next time they or someone they love is injured, rather than staying at home and trusting in god to sort things out. If doctors are so wrong, so useless, why bother with them?
In fact, lets get those defibrillators out of public buildings, and ban anyone learning CPR. Its all unnecessary if god is around to take a hand.
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Alternative tack: if this was TRULY a miracle, then their god has clearly and demonstrably shown that he can and will bring people back to life, can and will intervene directly in the world. Which means that EVERY person who dies and does NOT come back, died because god wanted them to. Every person who gets raped or beaten or starved or abused, has it happen to them because god specifically decided to stand back and let it happen.
This "miracle" pisses all over the "god can't reveal himself because of free will" argument. There is a big part of me that says we should accept this event as a genuine miracle from god, agree with the believers that that is what it was - and then push them on the questions that arise from it. A genuine miracle gives them nowhere to go with a lot of their apologetic excuses.