Sitting meditation is the method of great liberation; all the teachings flow forth from this, myriad practices are mastered this way. All the buddhas and bodhisattvas have entered and left by this door.
"What does it mean that sitting meditation is the root source of all the teachings?"
Meditation is the inner mind of the enlightened ones, discipline is their outer character, doctrine is their speech, Buddha remembrance is the invocation of Buddha's name; all come from the enlightened mind of the buddhas. Therefore it is considered fundamental.
"The method of meditation is formless and thoughtless; spiritual qualities are not obvious, and there is no proof of seeing reality, so how can we believe this?"
Your own mind and the enlightened mind are one. If you do not know your own mind, on whom can you call for witness and proof? Other than seek the identity of mind and Buddha, what proof do you seek?
"How should we practice this method? Even if we practice we are not sure of attaining enlightenment and fulfilling buddhahood; and if it is uncertain, even if we do practice, what is the benefit?"
The enlightened mind itself basically has no delusion or enlightenment. This is actually the subtle art of those who realize thusness; even if you don't become enlightened, when you sit once in meditation you are a Buddha for that sitting; when you sit for a day in meditation, you are a Buddha for a day; when you sit in meditation for all your life, you are a Buddha all your life.
"How should I rest my mind, how should I use my mind?"
The enlightened mind has no attachment to appearances; detachment from appearances is the character of reality. Among the four modes of conduct, walking, standing, sitting and lying, sitting is considered to be stable and tranquil. This means sitting straight and contemplating the characteristics of reality.
"Please explain in detail the meaning of sitting straight and contemplating reality."
Sitting straight means sitting cross legged as the Buddhas do; contemplating reality means sitting meditation, forming the symbol of absorption in the cosmos (left palm up, left hand on right palm, thumb tips joined to form a circle, symbol of the body of reality with no lack or excess, beginningless and endless, perfect and complete as a sphere), body and mind unmoving. Eyes half open, watching over the tip of the nose, you should see all compounded things as like dreams, illusions, bubbles, shadows; don't get hung up in thought about them.
"Why keep the eyes half open, watching over the tip of the nose?"
When the eyes are open and you can see for a distance, your mind can be distracted by the profusion of objects; yet if you close your eyes, you fall into a state of darkness and oblivion, and your mind is not clear. When your eyes are half-open, your thoughts don't race; mind and body are one thusness. This is called fulfilling buddhahood right where you are, the meaning of great capacity and great function.
"Though I hear what you say, it's still hard to really believe. I have heard that to attain wisdom, I need to accumulate virtue through reading and reciting the scriptures, fasting, discipline and recitation of Buddha names. How can there be anything special about peaceful meditation without doing the other practices?"
Practicing without any sense of attainment is called the exceedingly profound transcendent wisdom; this wisdom can cut off the source of birth and death like a sharp sword. To practice virtue in hopes of reward is the illusion of ordinary people. If you practice the way of unity of cause and effect, you realize buddhahood in one lifetime.
Watching the breath or counting the breath is, in fact, contemplating impermanence. Breath, body movement, and numbers: all continuously change from moment to moment. Thoughts, as much as anything else, continuously arise and perish. The idea of self is generated by thoughts; or rather, from attachment to thought. How do we attach to thoughts? We identify with our opinions and defend them, for instance. But tomorrow our opinions and point of view will change.