Pope Francis said:
"Merton was above all a man of prayer, a thinker who challenged the certitudes of his time and opened new horizons for souls and for the Church. He was also a man of dialogue, a promoter of peace between peoples and religions."
... words in an address before US Congress.
What certitudes of his time, exactly, did Thomas Merton challenge? What new horizons did he open up for souls and the Church?
I very much doubt that it had anything to do with him speaking up for the traditional and timeless truths of the Catholic Church. Wasn't he an existentialist? Wasn't it all about spiritual "experiences" for him?