What is the object of discernment? Does discernment mean only finding what is best among options that are all good? Or does it refer also to distinguishing morally good choices from morally bad choices? As noted previously, Fr. Peter in his article on discerning personal vocation, attributes to discernment only the apprehension or determination of the best out of several good choices.
The meaning of discernment
First we should consider the meaning of the word "discern" and "discernment". The fundamental meaning of "discern" is to mentally or sensibly distinguish something from others. And of course we should not only distinguish the best choice from other good choices, but should, indeed must distinguish good choices from bad choices. So discernment does include also, as most fundamental, perceiving the difference between what is truly good and what only seems so, between what truly comes from God or leads to him, and that which comes from our selfishness or leads away from God.
Discernment in Scripture
St. Paul also uses the term this way: "solid food is for the mature, for those whose faculties are trained by practice to discern good and evil" (Heb 5:14). In another traditional text linked with discernment, St. John says, "do not believe every spirit, but test the spirits to see whether they are of God" (1 John 4:1). Here the main distinction to be made is not between a spirit that moves one to something good, but not all that good, and a spirit moving one to the best ways of thinking and acting, but the fundamental distinction or discernment to be made is between the good Spirit, the Spirit of God, and an evil or false spirit, which is not from God.
Discernment and Prudence
It is important to bear in mind this general notion of discernment, in order to avoid making it excessively obscure and mystical. Of course, when the question is discerning God's will, there will always be some mystery, because God himself is a mystery to us, who walk by faith. Nevertheless the connection between discernment and ordinary Christian prudence is important for the practice of discernment. The ordinary means of discernment is prudence enlightened by faith and motivated by charity, the "faith that works through love" (Gal 5:6). The Catechism of the Catholic Church says, "When a prudent man listens to his conscience, he can hear God speaking" (n. 1777). And Vatican II says about priestly vocation: "The voice of the Lord who is calling should not in the least be expected to come to the ears of a future priest in some extraordinary manner. Rather, it is to be understood and discerned by those signs by which the will of God is made known daily to prudent Christians" (Presbyterorum Ordinis, n. 11).