Please keep in mind that every vocation is a mystery, and thus every man passes through these stages differently on the way to priesthood.
Some will pass through the first few stages only to discern that God is not calling them to priesthood. Others will keep going all the way to ordination.
Stage 1: The Initial Call
A man in stage 1 has recently experienced an attraction to priesthood for the first time. This initial stage of discernment often takes place during childhood, perhaps at Mass, in a Catholic school classroom, or when a priest invites a man to consider priesthood.
In this stage, a man feels an initial, mysterious attraction to become a priest, made all the more mysterious since he has almost no information about priesthood, discernment, or seminary.
The primary emotions are excitement and wonder. “Could God really be calling me to be a priest?”
Stage 2: Latency Period
A man in stage 2 has now been thinking about priesthood for some time, usually a few years, depending on when he entered stage 1. He is not thinking about it every day, however.
Rather, more days pass when he does not think about it at all. The idea surfaces from time to time, usually at Mass, while praying at night, or when another person mentions it. He has not convinced himself that priesthood is a real possibility.
Sometimes a man in stage 2 will prematurely “decide” that he is not being called to priesthood.
Stage 3: Assessment Period
A man in stage 3 realizes that his attraction to priesthood will not go away, even though he has tried to avoid it.
This man is now making a more serious effort to grow in his faith and prayer life. He may find a spiritual director because he realizes that he needs help discerning. He begins to fight the spiritual battle of surrendering to the will of God; some days he wins the battle, and other days he loses.
This man’s love for God is maturing and he begins to understand the joy of laying down his life for Jesus and his Church. His desire to serve others is growing, and he experiences happiness while serving.
A man in this stage is assessing specific fears now: the fear of celibacy, the fear of not being a holy priest, the fear of loneliness, and the fear of preaching in front of people.
Stage 4: Discernment Shift
A man in stage 4 is moving quickly towards surrender and resignation to the will of God. He has been faithful to prayer, attended retreats, gathered information, and has come to the conclusion that God is probably calling him to be a priest.
He feels a sense of peace should this be his God-predetermined vocation.
His spiritual director and vocation director are telling him that he has the signs and qualifications. He still may be hoping that God is only calling him to seminary for a year or so, but not to priesthood.
The essential element of stage 4 is the knowledge that discernment cannot proceed any further outside of seminary. He is just spinning his wheels.
Stage 5: Seminary Discernment
A man in stage 5 has been accepted as a seminarian by his bishop, and the bishop has assigned him to a specific seminary. I usually associate stage 5 with the first two years of seminary, either college seminary or pre-theology.
This is a very important stage in discernment. He now has a developed spiritual plan of life: he is going to Mass every day, praying before the Blessed Sacrament, and seriously studying the faith.
He is living in a seminary, surrounded by other men who are also discerning diocesan priesthood.
Stage 6: Consistent Peace
This man has been in seminary from two to four years and he has grown tremendously in faith, prayer, knowledge, and generosity. This man knows Jesus personally. He has spent countless hours in prayer and study and he is very capable of teaching others about Christ.
The excitement of those early years in seminary are over and he is now doing the hard work of priestly formation through daily prayer and study. This man is accustomed to the idea that he is very likely going to become a priest.
He knows himself much better now, and knows that he can fulfill the duties of a priest.
Stage 7: Moral Certitude
Stage 7 begins at the very latest when a man arrives back at the seminary to begin third theology. This is not really a stage of discernment so much as an end to discernment.
A man in stage 7 is no longer asking God if he should become a priest or if he has the gift of celibacy. He is preparing to be ordained a deacon at the end of third theology and then, one year later, a priest. This man has achieved moral certitude that this is God’s will.
He is not absolutely certain, because that is not possible, but he has received every indication that he should become a priest.