Chan sect teaches “understand the mind and see the nature” every day. The word “nature” of it was the empty matter. “understand the mind” means making us understand our heart is false because we become greedy for our stupid desires, causing admiration of self and then having the moment of birth and death.

 Straightly speaking, “understand the mind and see the nature” means to conquer the moment of birth and death, ending birth and death. (From Words of Chan by Shi Yongxin)