An interesting article titled "Celtic Monasticism as a Metaphor for Thomas Merton's Journey" by Paul M Pearson. on the Thomas Merton Society's site...
Merton found in Celtic Monasticism and in The Voyage of St. Brendan, in particular, a way of understanding monastic life and his own monastic life and this was why he was so fascinated by this subject and saw in it, as he says in a letter to Dame Hildelith Cumming, a "symbolic tract on the monastic life."
The metaphor of journey is widely used in understanding the Christian life and it is also a metaphor frequently used by and about Merton. It is a metaphor that covered his physical travels of his early life before entering the monastery and his final pilgrimage to the East, it covered his continuing conversion of life as a monk, his conversion to compassion and his conversion to his fellow human beings. Journey was also the metaphor he used to understand his search for God and for his true self.
Alongside such metaphors as solitary explorer, guilty bystander, stranger, wanderer, marginal person, Merton also used the metaphor of pilgrim of himself. In his Asian Journal Merton refered to himself as a pilgrim - "I have left my monastery to come here not just as a research scholar or even as an author. I come as a pilgrim...to drink from ancient sources of monastic vision and experience."