Reader's Question: "Is Zen dangerous, as an admixture to a pure Christianity? I've always been attracted by the meditation practice and the idea of unexpected sudden enlightenment through nonrational means, but the insistence on a fundamental unreality (mu) seems nihilistic at best."
My Answer: I think Zen probably is dangerous for Christians, in the sense that it is aiming at something altogether different from Christian goals.
Zen is aimed at detachment, Christianity aimed at Love - these are very different.
Zen meditation is aiming at a particular psychological state - Christian meditation at some kind of communion with the divine.
Having said that, it depends on how seriously Zen is practiced - I could imagine a moderate usage of Zen techniques from time to time would be compatible with an overall Christian life and even potentially helpful in a 'therapeutic' sort of way; but pursued rigorously (and successfully!) Zen clearly is not compatible with Christian theosis: they are two different things pointed in different directions...