The best book I have read about the similarities between Catholic and Zen meditation. Two sources for his main thesis that he mentions over and over are: Aquainas' Summa Theological and the Cloud of Unknowing, which is by an unknown author.He was an Abbot of a Benedictine Monastery in Rhode Island.

The transcript of a Sermon he gave on the same topic can be found at: http://www.studiesincomparativereligion.com/public/articles/On_Meditation-by_Dom... if you want the quicker version of his thoughts from the book it is a good place to start. ( )

Lately got in to zen so have been rummaging through some works by Catholic priest-intellectuals from as far back as the mid 60s (besides Merton)for insight on tying together East and West. I was as brainwashed a cradle Catholic as any, which breeds some considerable resentment covering up that guilt thing, so this is important, nay vital, for me and meditation's fruits (or fruitlessness) are fond fodder for the moment, which is all we have. There's nothing like practice, though. Two which have resonated with me so far are the almost prescient "Zen Catholicism" (1963) by Dom Aelred Graham--a British Benedictine monk--and Heinrich Dumoulin--a German Jesuit who lived and worked in Japan, author of numerous works tying zen in with Christianity, for any who are interested hereabouts.