Why were heretics burnt?
Burning was the punishment under ancient Roman punishment for treason after crucifixion had been abolished in the fourth century. It was consequently used by the Holy Roman Empire to deal with traitors and heresy was widely seen as a particularly serious kind of treason. Although the church never specifically sanctioned burning once a heretic had been relaxed to the secular arm, it was always perfectly well aware that this would be the result. If the heretic confessed after sentence had already been passed then it was usually commuted to strangulation by the executioner before the pyre was lit. In any case the victim often suffocated before the flames reached them although a skilled executioner could prevent this if instructed. In some jurisdictions burning was not the punishment used, for example the Venetians drowned traitors and heretics).
