20240901 心

 we don't know how we retrieve our memory, but when someone talks about a past event, we can recall it, the sound the picture, and the feeling as well. This is the use of the heart (心之用). 

From the use of the heart, we know the essence of the heart (心之本). However, we never know how the essence of the heart looks like. 

Remember, in ancient times, people don't know anything about the biology of the brain. They know there is a brain but how it works, and the function of different parts of the brain, they never know. The brain is like a black box, it cannot be described.

in Taoism, it mentions that the essence of Tao cannot be seen and heard, but we are so sure its present because we can see, and hear its use.