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:
A Whether there is any entirely spiritual creature, altogether incorporeal?
A Supposing that an angel is such, we ask whether it is composed of matter and form?
A We ask concerning their number.
A Of their difference from each other.
A Of their immortality or incorruptibility.