It is not in virtue of its liberty that the human will attains to grace, it is much rather by grace that it attains to liberty.
Saint AugustineAngels are spirits, but it is not because they are spirits that they are angels. They become angels when they are sent. For the name angel refers to their office, not their nature. You ask the name of this nature, it is spirit; you ask its office, it is that of an Angel, which is a messenger.
Saint Augustine