There are some problems in the apparently simple practise of finding the posture.

The way we do it is using the same ability of proprioception and feeling that we use to walk upright, to swim and run. But if those qualities were reliable, none of us would walk with stoops or hunch over our computers, none of us would be depressed or unnecessarily angry. We'd find ourselves straight and simple in all our activities. So how can we find the posture? How can we find it not merely on the cushion but everywhere in our experience?

Our practise is not a physical one. It is not a mental one. It is a practise based on real activity in the real world. The agent for this is a psychophysical unity which cannot be separated from its environment, from its experience. What that unity actually does, affects everything in it's experience, it fundamentally changes the nature of existence. In this instant, we are completely free to act and if we choose to accept the truth, there is a great responsibility in that action.

Our answer to this, as sitters or Buddhists or whatever you want to call it, is to accept the real nature of our existence as we experience it. In order to do this we have to stop doing things that prevent us from accepting the real nature of existence. We find a point of balance, not aggressive not passive, not overfed not underfed, not optimistic not pessimistic - we find the middle way that corresponds to the real state of our experience. It is a point where all attributes, all opinions vanish and there is only real experience that we can respond to as the circumstances require without bringing something complicated and constructed called our 'selves' to act for us.

But, if we accept zazen as the standard for our experience then our human problems of unreliable proprioception and feeling are crucial. They are the biggest problems in practise. How can we find the posture in experience? Continual practise? Working with a good teacher? Both those things certainly but ultimately, this is the question we are always asking. Perhaps the value is in simply continuing to ask the question that cannot be answered.