There is just no guarantee. Philip, about whom we read in today’s gospel, has spent a significant period of time with Jesus, and yet he simply has not grasped the simply concept that there is a powerful relationship between the Son and the Father. I am not sure why, but I do feel some sympathy for Philip. See, for me, the belief in the Trinity was a given. I have to confess I did not give it much thought, and in some ways, I still have not. This trinitarian understanding of God was just always the way it was.
But in recalling Saint Athanasius, whose feast we celebrate today, we are invited to remember that it was not always so. While he may not have been the easiest to get along with, his words and works helped to develop in a convincing way the belief of God as three persons, one God. This mystery of the Incarnation, then, has been really developed and settled.
But this took centuries for the Church to work out, and so it is not unreasonable that Philip might not have absorbed all of its meaning right away. But what he did absorb was the importance of remaining in relationship with Jesus. Even though Jesus sees him at his worst, he continues to love him, and Philip remains because there simply is no where else to go. He cannot find the fulfillment he has discovered in Jesus anywhere else, a fulfillment that he does not always understand, but comes to believe nonetheless.