“A vocation is not open to empirical investigation. The Lord is relentless when he wants to enlist someone in his service; but he is also incredibly self-effacing. One cannot possibly understand the signs of a vocation unless one remembers that god, because He is Love, woos souls with all the delicacy and shyness of a lover. Even those who can say that they never had the slightest doubt about their vocation still feel overwhelmed and at a loss to explain exactly what this means. For here contradictory truths inaccessible to ordinary human logic, come together: there is a sense of being led by someone stronger than oneself, and yet remaining free; the feeling that it will pursue us in season and out of season, and yet that it is within our power at any given moment not to heed it; the understanding that god has need of our so-operation to lead us wherever He desires. Mary was free to say no to the Angel.
Moreover, God’s call comes to us in a human context which may be ambivalent and need sorting out: family circumstances; the influence of a priest or of relations or friends; an example one feels impelled to follow; a book we have read, or a felling; psychological or emotional events. All these can be exploited by the Lord to incline us to follow His path”