The doctrine of angels is not currently one of the most studied parts of Aquinas's thought, and this goes a fortiori for the topic of angelic speech. Angelology is often seen as an outstanding example of the barren metaphysical speculations that, allegedly, characterized (late-) medieval thought, or, at best, as a rather arcane curiosity that might be of some interest to specialists in the history of mentality, but is embarrassing to philosophical commentators. However, this humanist caricature of the scholastic discussion on angels does not do justice to the historical motives behind it or to its systematic importance. On the contrary, the scholastic views on the nature and operations of the separated substances originated from crucial philosophical and theological debates. Furthermore, they can still be of relevance to present-day discussions. Located in the hierarchy of being below God but above corporeal creatures, in particular, human beings, angels offered to medieval scholars an important clue for their reflections both on God and on human beings.