Campanella treats the same subject at length in On the Sense of Things; so do Albertinus the schoolman; Jacob Naclantus, who handles it in four questions in volume 2 of his works; Antony Brunus; Aonius Palearius; Marin Mersenne; and many others.

This rational soul, which Augustine calls a spiritual substance that moves itself, is defined by philosophers as the first substantial actuality of a natural human body furnished with organs, through which a person lives, perceives and understands, acting freely and by choice. From this definition we may gather that the rational soul includes the powers and performs the functions of the other two, which it contains. All three faculties make one soul. In itself it is independent of organs and incorporeal, although it is present in every part, using the organs and working through them.

It is divided into two principal parts, differing only in function, not in essence: understanding, the rational power of apprehension; and will, the rational power of movement. All the other rational powers are subordinate to these two and fall under them.