Now we consider the distinction of corporeal and spiritual creatures: firstly, the purely spiritual creature which in Holy Scripture is called angel; secondly, the creature wholly corporeal; thirdly, the composite creature, corporeal and spiritual, which is man.
Concerning the angels, we consider first what belongs to their substance; secondly, what belongs to their intellect; thirdly, what belongs to their will; fourthly, what belongs to their creation.
Their substance we consider absolutely and in relation to corporeal things.
Concerning their substance absolutely considered, there are five points of inquiry:
A1 Whether there is any entirely spiritual creature, altogether incorporeal?
A2 Supposing that an angel is such, we ask whether it is composed of matter and form?
A3 We ask concerning their number.
A4 Of their difference from each other.
A5 Of their immortality or incorruptibility.