Shinjin Datsuraku : Dropping body and mind : These words have been misunderstood so much throughout the ages. The misunderstanding is due in part to the fact that these words are related with the function of the autonomic nervous system. Prior to the 19th century, human beings did not have any knowledge about the autonomoc nervous system, and so they did not know the true meaning of dropping body and mind. But the true meaning of dropping body and mind is very much related to the function of the autonomic nervous system.

The autonomic nervous system is divided into two parts, they are the sympathetic nervous system and the parasympathetic nervous system. Often these two functions are imbalanced, in conflict, one emphasized over the other. For example, if the sympathetic nervous system is emphasized too much and is imbalaced, we may be prone to too much activity, too much thinking, even anxiousness. If the parasympathic is emphasized too much and is imbalanced, we may be prone to being dull, lethargic, lazy, lacking self-motivation. But when we are practicing Zazen,the strength of the sympathetic nervous system, and the strength of the parasympathetic nervous system become equal, balanced. And we automatically have the consciousness that the function of the sympathetic nervous system, in its extreme forms, has vanished, and the function of the parasympathetic nervous system, in its extreme forms, has vanished.

Therefore in Zazen, when our autonomic nervous system has become balanced, the situation of the autonomic nervous system seems to be as if it were in a state of “plus/minus=zero.” So we have consciousness as if our body and mind have been lost. This does not mean that the balanced state of Zazen is a blank nothingness, that the sensate ability of the body no longer exists, that the thinking ability of the mind no longer exists. Rather, it means that the balanced state of Zazen is the end of living in a state of extremes, the end of one side being emphasized too much over the other, the vanashing of life out of balance. This is the true meaning of Dropping body and mind, or Shinjin Datsuraku. Of course, there was no knowledge of the autonomic nervous system before the 19th century, and so it was very natural for human beings not to have a true interpretation of Shinjin Datsuraku, or Dropping body and mind, before the 19th century.

We may also understand the dropping of body and mind as representing the dropping of both the materialistic and idealistic/spiritualistic points of view.