The good angels are marshalled in a hierarchy of nine orders, to which they were assigned in order of merit at the beginning of the world, and to each of these a specified task is given. For example, the order named virtues (_virtutes_) has charge of miracles; and the business of the seraphim is “to veil the face and feet of God”.[111] The nature of the angels is described succinctly in a paragraph of the _Differentiae_: [111] _Etym._, 7, 5, 24. Angels are of spiritual substance; they were created before all creatures and made subject to change by nature, but were rendered changeless by the contemplation of God. They are not subject to passion, they possess reason, are immortal, perpetual in blessedness, with no anxiety for their felicity, and with foreknowledge of the future. They govern the world according to command; they take bodies from the upper air;[112] they dwell in the heavens.[113] [112] For appearance to man. _Cf._ Angeli corpora in quibus hominibus apparent, de superno aere sumunt. _Sentent._, 1, 10, 19. [113] _Diff._, 2, 41. The special virtue of the good angels is subjection to God. “There is no greater iniquity for them than to wish to glory not in God but in themselves”.[114] The gaps in their ranks caused by the fall of the bad angels were to be filled from the number of the elect.[115] [114] _Sentent._, 1, 10, 16. [115] _Sentent._, 1, 10, 13. The demons, or bad angels, were created along with the good; indeed the devil, their leader, was first created of all the angels. It was “before the time of the visible universe” that their fall took place; at that time they lost “all the good of their natures” and all possibility of pardon.[116] They are the “enemies of mankind” and are “sent on the service of vengeance”. The only restraint on their malignity is that they are obliged to obey God. Isidore sums up their activities in a fear-inspiring way: [116] _De Ord. Creat._, 8, 7–10. They unsettle the senses, stir low passions, disorder life, cause alarms in sleep, bring diseases, fill the mind with terror, distort the limbs, control the way in which lots are cast, make a pretence at oracles by their tricks, arouse the passion of love, create the heat of cupidity, lurk in consecrated images; when invoked they appear; they tell lies that resemble the truth; they take on different forms, and sometimes appear in the likeness of angels.[117] [117] _Diff._, 2, 41. Their capacity for evil tasks is increased by their superior intelligence, which retains “the keen perception of the angelic creation”.[118] Their power of foreknowledge, and, in addition, the duration of their experience, make the struggle against them a hopeless one for man. They are also incredibly persistent: “The devil never rests from his attack on the just man”, who is “sometimes reduced to straits of despair”.[119] [118] _Sentent._, 1, 10, 17. [119] _Sentent._, 3, 5, 35–36.