All the duties of spiritual beings, as much for angels as for men, consist chiefly in this proper usage; and it can be said without fear that if they use their freedom with care, without becoming slaves of lies and vanity, they are on the road to the greatest perfection of which they are naturally capable, provided, however, that their understanding does not remain idle, that they continually take care to urge it toward new knowledge, and that they make it capable of greater truths by continual meditations on subjects worthy of its attention.