In the parable of the sower (St. Matthew 13,1-23), our Lord tells us that His messages, His calls are received by men with different dispositions and thus yield different results. Why these different personal dispositions? Why do quite a few young vocationers present signs of insufficient growth in their vocational commitment during the years immediately following the initial formation in vocational settings? Why do some of these vocationers - and many of them in recent times - leave their vocational commitment? Why do quite a few priests and religious of both sexes, who initially did not show the foregoing signs of insufficient vocational growth, later on settle down in what couls be called a state of early retirement or of nesting in vocation, i.e., in the state of more or less apathetic routine in which only half of their potentials are used for the Kingdom? Many complex elements enter into the picture when one tries to find some clues toward an answer to the previous questions. The primacy of supernatural factors is not denied nor diminished here. Neither is the relevance of the ideas, functions and structures of the vocational institutions overlooked. But what about the dispositions of men of which our Lord speaks? Again, the complexity of the issues involved is staggering. The present book intends to bring a modest contribution to the multifaceted task of offering some clues related to these issues.