Well, it's already Valentines Day somewhere in the world, so it's probably a good time to take a look at the story of Valentine. That's the first problem, there was more than one Valentinus (a name that means strong and healthy), in fact there are a number of Christian Martyrs bearing this name. Valentine of Terni became the local bishop in 197AD and was executed during the reign of Aurelius. The priest, Valentine of Rome, was martyred around 269AD. Both were buried alongside the Via Flaminia highway, and the skull of the latter can now be seen in the Basilica of Santa Maria in Rome.
Valentine of Rome is the most likely candidate for the Saint Valentines story - a story which revolves around a Christian priest illegally marrying soldiers after an Imperial decree banned marriage - with the typical martyrdom results. Of course, the question is, would Valentine have been executed for marrying members of his church? First of all, this supposed ban marriages during 269AD. Right from the beginning of the professional Roman legion during the last decade of the 2nd-century BC, soldiers were not allowed to marry during the course of their 16 to 20 years of service, a situation that was still standing in 269AD when Valentine came along. A new and total ban on marriages across the Empire was at the very least superfluous, and the long standing military edict is the most likely origin for the the story.
Of course, then you've got to define a marriage - obviously it would have to be recognised by the state and since the Christianity wasn't sanctioned by the Roman state in 269AD, it seems pretty unlikely a 'Christian' marriage would have been recognised as an official marriage. As such, from a Roman legal point of view, Valentine may have been going through the motions of marriage, but the couples were not actually married - thus no law was broken. And no matter how crazy Christian stories like to paint the extremes of Roman law enforcement, if it's not illegal then Valentine wasn't going to end up in a lion's cage.
So was Valentine executed? Well, he may have been, another part of the story says upon meeting Claudius the Second to plead his case, he tried to convert the Emperor - a situation that led to a summary execution. Technically, Christians weren't being executed for being Christians in 269AD, they were being executed for treason. The 250AD "For the safety of the Empire" edict of Decius required citizens to conduct sacrificial offerings before local magistrates to receive a 'certificate of loyalty to the ancestral gods' - in other words to hold a certified oath of loyalty to the Empire. Anyone not holding this certificate could be construed as an enemy of the Empire...thus a sticky end. If Valentine was executed, this is the most likely reason for his martyrdom.
As for how Valentines Day got to be so romantic? Well, you'd have to ask Chaucer that, he popularised the day in 1382 when he wrote "For this was on Saint Valentine's Day, when every bird cometh there to choose his mate."
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