The difference between intellectual understanding and experiential realization is substantial. Experiential realization is the genuine attainment, where one can personally observe the true suchness of their own mind in the present moment; what is observed is factual, it is direct perception. Intellectual understanding is merely comprehending the principles, feeling that the Tathāgatagarbha is like that, without having personally realized it. Therefore, one cannot observe true suchness directly in the present moment. If one cannot genuinely observe and practice in accordance with reality in the present moment, it is impossible to truly turn towards and rely upon the true principle of suchness.
To better understand the difference between the two, an analogy can be used. Intellectual understanding is like studying theoretical knowledge about an apple. The theory can be studied quite well, possibly in great detail, including the apple's origin, variety, transportation, storage, appearance, shape, color, luster, and so on. Yet, since one has not personally tasted it, one does not know the true flavor of the apple, how sweet, moist, and palatable it is, and thus the body and mind do not receive its true benefit. Experiential realization is having personally eaten the apple, truly knowing its sweet taste; the experience of the apple is genuine and not false, and the body and mind have already gained benefit.
However, it is possible that the person who has eaten the apple may not be able to express its flavor well, let alone know various information such as its origin. Whereas the person with intellectual understanding may know all the theories about the apple but has never tasted a single bite. Thus, all their theories remain merely theories, providing no real benefit to their own body and mind. It is like the dullest disciple of Śākyamuni Buddha who attained the fourth fruition of Arhatship but could not explain the Dharma principles of the path to liberation. Yet, he had already achieved genuine liberation, truly ended birth and death, transcended the cycle of saṃsāra, and would not experience the slightest suffering in the future. In contrast, ordinary people today possess strong theoretical knowledge. Not only can they talk eloquently and produce volumes of writings, expressing themselves like sages, but within their hearts, there is not even a shadow of liberation. While speaking like a sage, they act entirely like ordinary beings. The greed, hatred, and delusion within their minds remain completely unsubdued; their arrogance burns fiercely, and others dare not provoke them at all.
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