The monastic ideal of “leaving home” is repeatedly praised by Master Dogen in the ordination ceremony known, in Japanese, as “Shukke Tokudo” — which translates as something like “leaving home, sharing the dharma.” In lay practice, we do not literally leave home, of course, other than for the occasional extended retreat, or sesshin; but we interpret the meaning as deeply significant. Our true home turns out to be unrelated to geography, or any other relative circumstances of existence.
We might also question the reality of home-leaving in the life of monastics, as Master Dogen mentions regarding monks of his time (see Shobogenzo Zuimonki). He suggests that some cannot really relinquish their attachment to family, and all that it entails, for the sake of Zen — or “hearing the true Dharma” as he puts it in Dogen’s Vow (Eiheikosohotsuganmon).
Others, who are able to do so, are not able to let go of their attachment to their body and good health. They are not willing to put their life on the line, which is, after all, understandable — in this same poem he quotes Ch’an Master Lungya: “In this life save the body; it is the fruit of many lives” — but I take his point to be that the obsession with living the good life, at the expense of Zen practice, is ultimately doomed to failure. Aging, sickness and death, the three major marks of existence, according to Buddhism, cannot be avoided in the long run. And Zen takes the long view.
But the third and most difficult level of non-attachment that Dogen Zenji stresses, is to our own ideas and opinions. Even monks who can realize the first two levels have difficulty with this last, clinging to their erroneous worldview. The monk who can do so has the best chance of waking up during this lifetime.