This is an exposition of the teachings of saints. The way pointed out by the sage is to explore the essence of the heart, and the noumenon of man is the truth after all. As for what this truth is. It is the unity of knowledge and action. Is to concentrate all your thoughts and just do things. For example, filial piety, have the heart to do this. Not easy to do. It is even harder to do it well. It is truth because it can destroy illusions and fallacies.