Tosotsu's teachings were thus :
Of the three barriers, the first barrier is studying Zen. The objective of studying Zen is to see one's true nature. Now where is your true nature?
The second is that when one realizes his true nature, he will be free of birth and death. Now how can you free yourself when you shut the light from your eyes and becom a corpse?
Thirdly when you are free of birth and death, you should know where you are. Now when the body dissolves into the elements, where are you?