How does one know if God is calling him to be a priest?
All that D.J. Clayworth has posted in his answer is correct, yet it is somewhat incomplete.
Having been in a seminary for a number of years myself, I can say that the time in the seminary itself is simply a time of discernment for both the the individual and the Church.
The vocation to the priesthood is a calling from God and until the very moment of ordination their is in a sense no absolute way to determine one’s calling.
There are signs or indicators that one may be called to the priesthood:
- Celebacy is easily maintained
- A genuine prayer life is naturally obtained.
- The Divine Office is prayed faithful at the point a seminary enters his theological studies (post philosophy studies years).
- His scholastic studies are maintained at a certain level.
It should be noted that seminaries will also make a write recommendation to the Seminarian’s bishop for ordination to the deaconite and priesthood. Negative reviews do happen, but in the end it is the bishop and his advisers, who make the call. The only negative review from a seminary that I am aware of, the bishop in question actually proceeded with the ordination anyway: the phrase that the seminarian was too traditional was overlooked!
Even with all these lined up in the right way, on can not absolutely I have an vocation to the priesthood until one is actually called by the bishop to be ordained.
This is seen in the actual Rite of Ordination:
Rite of Ordination
When all has been prepared, the candidates are called forward by a Deacon. THe candidates are then presented to the Bishop by the Vicar for Vocations.
Vicar: Most Reverend Father, holy mother Church asks you to ordain these, our brothers, to the responsibility of the Priesthood.
The Bishop inquires as to the worthiness of the candidates.
Bishop: Do you know them to be worthy?
Vicar: After inquiry among the Christian people and upon the recommendation of those
responsible, I testify that they have been found worthy.
After judging them worthy, he elects them for ordination.
Bishop: Relying on the help of the Lord God and our Savior Jesus Christ, we choose these men, our brothers, for the Order of the Priesthood.
All present: Thanks be to God
It is only after this point can the Church and the individual to be ordained know for sure that they have a vocation from God to minister to the People of God.
Seminary studies are generally for eight years of post secondary school (four years of philosophy and four years of theology). That is lots of time for discernment!