There exists among the angels some manner of speech; for to speak to another is simply to manifest to him the concepts of the mind. Thus the angels are said to speak when they direct their conceptions to others for the manifestation of their will. In like manner, when our mind turns to the actual consideration of what it possesses habitually, it is said to speak to itself; for even the interior conception of the mind is called a word.
And the inferior angels can speak to the superior; for although every illumination is speech, the converse does not hold; thus the manifestation of things which depend upon the intelligent will is not illumination, but only speech, while something which is conveyed from God, Who is the Principle, through a superior angel to an inferior one, is illumination. But although this ordering of their mental conceptions one to another constitutes the speech of the angels, it is not thus that they speak to God, Who is the Creator, and principle of all truth and all will. For a person approaches another in a different manner if he desires to receive something, as a disciple comes to a master; and the angels speak to God as consulting the Divine Will for action, or as admiring His excellence, which surpasses all understanding.
Local distance forms no impediment to the speech of the angels, since this consists in an intellectual operation which is independent of time and place. For the angels do not understand by means of phantasms as we do, therefore distance of place and time do not affect them. But the speech of the angels to each other is not known to or understood by all; for an angel may have occasion to direct its mental conception to one rather than to another; and so it would be perceived correspondingly. For speech being related to the principle of created will, which is proper to each one, does not belong to the same order as illumination, which emanates from God, the primary source of truth and the principle common to all; hence it is not necessary that these locutions should be common to all.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni