The book of Revelations describes the final days before the second coming of Christ as a time when the antichrist’s representative will “force all people, great and small, rich and poor, free and slave, to receive a mark on their right hands or on their foreheads, so that they could not buy or sell unless they had the mark, which is the name of the beast or the number of its name” (Rev 13:16-17 NIV). It has always seemed peculiar to me why one would choose to have something placed on one’s forehead if given the choice of one’s hand. Perhaps a better understanding is that at the time of John’s vision(s), it was unclear which anatomical location would be the obligatory place for the mark. It is also possible that a change in regime will change the required location of the mark such that some people could have two marks (one in each location), or that the location of the mark will change such that all subsequent marks will be in the new location but those with pre-existing marks will not be required to be re-marked. These scenarios could have given John the sense that it was optional, but I am not sure that the option will exist. Furthermore, most readers tend to interpret the mark as a literal mark. It could just as easily be an invisible mark such as a sub- or intra-dermal RFID tag just like the ones currently used to “chip” pets.