Christian apologetics has taken many forms over the centuries. In the Roman Empire, Christians were severely persecuted, and many charges were brought against them. J. David Cassel gives several examples: Tacitus wrote that Nero fabricated charges that Christians started the burning of Rome. Other charges included cannibalism (due to a literal interpretation of the Eucharist) and incest (due to early Christians' practice of addressing each other as "brother" and "sister"). Paul the Apostle, Justin Martyr, Irenaeus and others often defended Christianity against charges that were brought to justify persecution.