controlled by the Levites as being cities of refuge, although they considered that asylum could only be claimed against the will of a city's inhabitants if the city was one of the six main cities of refuge. Although there the six main cities of refuge were named in the Bible, the Talmudic sources argued that other cities could, over time, be officially substituted for these six, to take account of changing political circumstances. The substitute cities of refuge were constrained to be only of moderate size, since, if they were too small, there could be scarcity of food, forcing the refugee to imperil himself by leaving the city to find sustenance, and, if they were too large, then it would be too easy for an avenger of blood to hide in the crowds; nevertheless, the surrounding region was required to be quite populous since that way, an attack by the avenger of blood could be more easily repelled. The altar of the Temple in Jerusalem also came to be regarded as a place of sanctuary, but only counted for the officiating priest, and even then only temporarily, as the priest ultimately had to be taken to a city of refuge; when Jerusalem was under Seleucid control, Demetrius I offered to turn the Temple into an official place of sanctuary, though the offer was turned down. The rabbinical sources differentiated between four forms of killing, sometimes giving examples: Complete innocence, for which no further action was necessary. This situation arises when someone is killed while the perpetrator is fulfilling his legal duties such as corporal punishment; for example, a father who strikes his son, a teacher who disciplines/chastises his student, and an agent of the court deputized to flog transgressors. Negligence, which required exile to a city of refuge. This situation arises when someone is killed as a result of legal activity, which the perpetrator was not required to perform. Severe carelessness, for which exile is insufficient. This situation arises when someone is accidentally killed as a result of illegal activity by the perpetrator; for example, this situation arises if a shop owner fails to maintain their property, and it collapses and kills a legitimate customer. Murder, which was subject to the death penalty. According to classical rabbinical authorities, the cities of refuge were not places of protection, but places where atonement was made; Philo explained this principle as being based