While the concept of Heaven ("malkuth hashamaim" מלכות השמים, the Kingdom of Heaven) is much discussed in Christian thought, the Jewish concept of the afterlife, sometimes known as "olam haba", the World-to-come, is not discussed so often. The Torah has little to say on the subject of survival after death, but by the time of the rabbis two ideas had made inroads among the Jews: one, which is probably derived from Greek thought, is that of the immortal soul which returns to its creator after death; the other, which is thought to be of Persian origin, is that of resurrection of the dead.