When one is skilled and adept at something, what role does the manas play in it? In worldly terms, mastering a skill requires both theory and practice. From the perspective of the Buddha-dharma, theory is the mind consciousness's understanding, while practice is the manas's realization. Skillfulness is the result of repeated practice that perfumes the manas; moreover, there must also be wise contemplation and the summarizing of experience, so that the manas's wisdom is elevated and its mental factors are transformed—only then can skillfulness be achieved.
For example, in learning to ride a bicycle, even if you memorize the theory of cycling inside and out, you still cannot ride. You must get on the bike and practice repeatedly before you can ride. The body's operations are directly controlled by the manas with the cooperation of the tathāgatagarbha. The process of practice is precisely the process of using the mind consciousness's thinking to perfume the manas. Once the manas has been repeatedly perfumed, it operates the body with great proficiency. At this point, the mind consciousness need not focus on the matter of riding at all, yet the bike is ridden just as steadily.
The manas directs the six consciousnesses in their operations; when its directing is proficient, the operations of the six consciousnesses are proficient. By what can the manas direct proficiently? From this it can be seen that it would be absolutely impossible for the manas to have no memory. If the manas had no memory, the mind consciousness could never succeed in perfuming it—the manas would forget the moment it turned away, and the mind consciousness's repeated practice would be useless. In later lives, upon encountering the right conditions, one would learn a certain skill very quickly—this is the manas's memory at work.
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