Why Do Thoughts Cease When Introspecting on One's Own Mind?

Question: When I introspect my thoughts, this awareness that observes the thoughts—is it the mind consciousness or the fundamental mind? I now suspect whether it is another mind consciousness of mine observing the thought that arises in the present moment. Why do I have this suspicion? Because I have had an experience: when I become aware that a thought arises in the present moment, that thought might originally have been a complete sentence, but when I first become aware of that thought, only half of it pops out and then disappears, cut off by my awareness. So this "awareness" that I believe cut what should have been a complete sentence into half a sentence—I wonder, could it be another mental thought? If it is another mental thought that cancels out the previous one, then is my method of introspection—my so-called awareness (as a third party)—wrong? Or is it using the mind consciousness to suppress thoughts?

Answer: The mind that can be aware of thoughts is not the fundamental mind. The fundamental mind does not know any dharma at the level of the mundane world, including the thoughts of the seven consciousnesses; yet the fundamental mind definitely can know the thoughts and various activities of the seven consciousnesses—only what He knows is not content at the level of mundane dharmas. Let us set this aside for now. Speaking only of the mind that can observe thoughts: on the surface, it is the solitary consciousness (mano-vijñāna-eka-citta). The solitary consciousness can observe—or one may call it introspect—its own thoughts.

When the mind consciousness introspects its own thoughts, the thoughts are of various kinds. If a thought is evil and unwholesome, at that moment the solitary consciousness knows that its own thought is bad, and the thought automatically disappears. If it is not like this—if the thought is a wholesome thought related to cultivation, or a thought that is neither wholesome nor unwholesome—then due to insufficient meditative concentration (samādhi), the attention shifts to the observing side of the consciousness, and on the observed side where the thought is, because the mental power is insufficient, the thought can no longer arise, and thus it ceases.

If this situation occurs during cultivation of the path, one needs to further strengthen the training in meditative concentration. Only when the power of concentration is sufficient can both the observing and the observed aspects of consciousness continue, maintaining balance—that is, the thoughts do not cease, and the observation does not cease either. In this way, one day wisdom will arise: on the one hand, one can be aware of whether thoughts are wholesome or unwholesome; on the other hand, one can be aware of the arising, ceasing, and abiding of thoughts, their suffering, emptiness, impermanence, and non-self, and one can also seek out the source from which thoughts arise—the fundamental mind.

In fact, during the introspective activity of the solitary consciousness, when the power of concentration is sufficient, there is also the introspection of the manas; that is, the mind consciousness and the manas jointly observe the mind consciousness and the manas. There is both self-observation and cross-observation, mutual observation. Only such observation is the ultimate observation, and only then can true power of awareness and wisdom arise.