Cute Young Red Haired Girl Wearing Red Stockings And Angel Wings

Philosophically, angels are "pure contingent spirits." According to Aristotle, just as there is a First Mover, so, too, must there be spiritual secondary movers. Thomas Aquinas (13th century) expands upon this in his Summa contra Gentiles and Summa Theologica.
Judaism
The Bible uses the terms מלאך אלהים (mal'akh Elohim; messenger of God), מלאך יהוה (mal'akh YHWH; messenger of the Lord), בני אלהים (b'nai Elohim; sons of God) and הקודשים (ha-qodeshim; the holy ones) to refer to beings traditionally interpreted as angels. Later texts use other terms, such as העליונים (ha'elyoneem; the upper ones).