Why Do Thoughts Stop Arising When Observing the Mind?

Question: When I introspectively observe thoughts, is this awareness that observes thoughts the conscious mind or the original mind? I suspect that it might be another conscious mind observing the thoughts arising in the present moment. Why do I have this doubt? I have an experience: when I become aware that a thought is emerging, it should have been a complete sentence, but as soon as I become aware of it, only half the sentence appears before it vanishes, cut off by my awareness. So, is this "awareness" that I believe cuts a full sentence into a half-sentence actually another thought? If it is another thought counteracting the previous one, then could my method of introspection—this so-called "third-party" awareness—be mistaken? Or is it just the conscious mind suppressing thoughts?

Answer: The mind that can observe thoughts is not the original mind. The original mind is unaware of any phenomena on the conventional level, including the thoughts of the seventh consciousness. However, the original mind can certainly perceive the thoughts and various activities of the seventh consciousness, though what it perceives is not content on the conventional level. We will set this aside for now. Focusing solely on the mind that observes thoughts, it is explicitly the manas-consciousness. The manas-consciousness can observe, or rather introspect, its own thoughts.

When consciousness introspects its own thoughts, thoughts can be of various kinds. If the thoughts are unwholesome or unvirtuous, the manas-consciousness recognizes that its thoughts are unwholesome, and the thoughts then automatically vanish. If not—if the thoughts are wholesome thoughts related to practice or neutral thoughts—then due to insufficient concentration, attention shifts to the observing consciousness. The observed end, where thoughts reside, lacks sufficient mental energy, so thoughts fail to arise and are thus cut off.

If this occurs during spiritual practice, it is necessary to further strengthen concentration training. Only when concentration is sufficient can both the observing and observed aspects of consciousness continue, maintaining balance. That is, thoughts do not cease, and observation does not cease either. In this way, wisdom will one day arise, enabling one to discern the wholesomeness or unwholesomeness of thoughts on the one hand, and on the other, to perceive the arising, ceasing, changing, and abiding of thoughts—their impermanence, emptiness, and selflessness—as well as to trace the source of thoughts: the original mind.

In fact, during the introspective activity of the manas-consciousness, when concentration is sufficient, there is also introspection by the manas (the seventh consciousness). That is, consciousness and manas together observe consciousness and manas, involving self-observation, mutual observation, and cross-observation. Only this kind of observation is ultimate observation, capable of giving rise to true awareness and wisdom.