When we sit zazen, anything can and usually does arise in our head; a childhood experience we want to suppress, an unpleasant experience of being criticized by someone, and wanting to reject the criticism, or thoughts of all the nice things we'd like to buy with our next paycheck or about how close to enlightenment we must be because of our good zazen. Despite or because of the fact that we are just sitting facing the wall, we feel uncomfortable and seek to entertain ourselves by forming pleasant thoughts to think about. This wouldn't be so bad if only pleasant thoughts formed, but rarely is that ever the case.
Very often, even when we're not sitting zazen, thoughts form somewhere despite our intention to reject or suppress them — thoughts of the demise of
a loved one (or, heaven forbid, our own death!), or our seeming loneliness, or the lack of a sense of meaning or worth in our lives.

When these thoughts continue to come up during one period of sitting or over a period of several sittings, or over a period of twenty or thirty years, we begin to become suspicious of them (even the horrible or frightening ones) and we begin to settle down and not be so pulled around by them. And living a life of just sitting deeper and deeper into ourselves without being carried away by our thoughts and emotions is living a life based on zazen. The more we practice a zazen of just letting come up whatever comes up and letting it go away, the more we realize that our thoughts are but a mirror of whatever it is that is foremost in our lives at any one time. It isn't that after sitting for many years fewer and fewer thoughts arise until we enter a state of thoughtlessness. Living thoughtlessly is a large part of the problem of our busy frenetic society today! It is in letting the thoughts that arise in our minds come and go as if looking into a mirror but without getting carried away by them (i. e, by trying to suppress, or reject or attach to them) , that the life force that runs through each and every one of us and everything around us straightens out our lives naturally, so that we are able to give full play to whatever the encounter before us calls for.

There is an expression in Zen that goes, munen musô — no thought, no form. That is, it is popularly believed that if a person sits zazen hard enough and for a long enough time, then one day he or she will arrive at a state of munen musô — no thought, no form — equivalent to satori or enlightenment. To be sure, there are times when one sits zazen that very few or even no particular thoughts arise, but such a psychological state should never be confused with Enlightenment. If a state of no thought, no form is the ideally "enlightened" state, then the rock out in the garden is far more enlightened that I am since it has no thought!

The expression, munen musô, very simply put, means giving no thought to "what's in it for me?" It means not being so tied up by conventional forms that we become unable to function. For example, to be so puffed up with pride over our position as top executive in the company that we literally lose our sight towards helping others around us either in the company or in our community at large. This is also the sense of the bodhisattva vow to save all sentient beings before trying to save oneself.

Zen Gardens: Kyoto's nature enclosed (Thomas Wright, Mizuno Katsuhiko)

munen musô