Penn (from Penn and Teller) had a video on his vlog "Penn Says" that basically supported proselytizing. The argument was that if you think you are right about an afterlife, supreme being, etc, you basically have a civil duty to tell the world.
This video has been used by a number of churches, which has trickled back to Penn.
In this video, Penn discusses some of the reactions to his post, including an experiment to test the efficacy of prayer.
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