and the Jabriyya against the Qadariyya, the Muʿaṭṭila against the Mumaththila—just as two rival states vie for sovereignty, or as the feuding clans of Qays and Yaman, and the like.

Whenever one faction gains the upper hand after having been wronged by another, it seeks to avenge itself; it does not stop at the limits of justice but retaliates in kind, wronging the other just as it had been wronged.

Thus the Christians, intent on contradicting the Jews, declared lawful whatever the Jews forbid—pork, for example. They even tested those who wished to enter their faith by making them eat pork: if the candidate ate it, he was accepted as a Christian; if he refused, they would not admit him.