All moral conduct may be summed up in the rule: avoid evil and do good. In the language of Christian asceticism, spirits, in the broad sense, is the term applied to certain complex influences, capable of impelling the will, the ones toward good, the others toward evil.
However, in the restricted sense, spirits indicate the various spiritual agents which, by their suggestions and movements, may influence the moral value of our acts. Concupiscence, disturbances of the imagination and errors of sensibility, thwart or pervert the operations of the intellect and will, by deterring the one from the true and the other from the good (Genesis 8:21; James 1:14). In opposition to our vitiated nature, or so to speak, to the flesh which drags us into sin, the Holy Spirit acts within us by grace, a supernatural help given to our intellect and will to lead us back to good and to the observance of the moral law (Epistle to the Romans 7:22-25). Besides these two spirits, the human and the Divine, in the actual order of Providence, two others must be observed. The Creator willed that there should be communication between angels and men, and as the angels are of two kinds, good and bad, the latter try to win us over to their rebellion and the former endeavour to make us their companions in obedience. Hence four spirits lay siege to our liberty: the angelic and the Divine seeking its good, and the human (in the sense heretofore mentioned) and the diabolical its misery.
"Discernment of spirits" is the term given to the judgment whereby to determine from what spirit the impulses of the soul emanate, and it is easy to understand the importance of this judgment both for self-direction and the direction of others. Now this judgment may be formed in two ways. In the first case the discernment is made by means of an intuitive light which infallibly discovers the quality of the movement; it is then a gift of God, a grace gratis data, vouchsafed mainly for the benefit of our neighbour (1 Corinthians 12:10). This charisma or gift was granted in the early Church and in the course of the lives of the saints as, for example, St. Philip Neri. Second, discernment of spirits may be obtained through study and reflection.
It is then an acquired human knowledge, more or less perfect, but very useful in the direction of souls. It is procured, always, of course, with the assistance of grace, by the reading of the Holy Bible, of works on theology and asceticism, of autobiographies, and the correspondence of the most distinguished ascetics. The necessity of self-direction and of directing others, when one had charge of souls, produced documents, preserved in spiritual libraries, from the perusal of which one may see that the discernment of spirits is a science of the Church.
Respecting the Boundaries of Knowledge: Teaching Christian Discernment with Humility and Dignity, a Response to Paul O. Ingram
Jan 01, 2011; NATURAL SCIENCE AND BUDDHIST PHILOSOPHY AND PRACTICE AS RESOURCES FOR CHRISTIAN SPIRITUAL discernment Boundary Questions...