Because in Zen, you see, we don't meditate on anything. We don't meditate on world peace, for instance, or loving-kindness, or forgiveness, or to acquire any of the lofty virtues that we or our dastardly neighbors so glaringly lack. Meditating on something else would just stoke the conflagration up top. We might be reminded — as if we needed reminding — of what we don't have, how we don't act, what we don't like, who said what to whom and how lousy we feel because of it. We meditate instead to quench the flame on our heads, to quiet the torment and silence the roar. That alone brings salvation, peace, love, and forgiveness. How? By itself. We have a wellspring of all that within us, a deep and eternal aquifer of fire retardant, when we give ourselves the breathing room to find it.
That's what we do in Zen meditation, or zazen. Breathe. Simply breathe, attending to our own breath as it rises and falls, fills and empties, counting it from one to ten and all over again just to give our brilliant brains something to do. We do this with our eyes open, looking at a wall or the floor in front of us. It's easy to think we don't know how to do it, and easy to think we're not doing it right, but this is the way to see that thoughts like that are just — oh yeah, look at that — thoughts, and we start counting again.
I read a simple anecdote that locked itself into my brain. I can't remember which author wrote it. Some people on a walk noticed a monk standing on a nearby hilltop. "I wonder if he lost something up there?", one said. "Maybe he is lost", suggested another. After more talk, one of the group walked up and spoke to him. "Are you lost?" "No." "Are you waiting for a friend?" "No." "Well, if you don't mind me asking, what are you doing?" "I'm standing here."
Steven Wright, that fascinating nut, says that sometimes he likes to go into a doctor's or dentist's waiting room and just wait.