Why is the wisdom of the mind consciousness greater than the wisdom of the manas?

The wisdom of the mind consciousness is far greater than that of the manas. One reason is that the objects cognized by the mind consciousness are far fewer than those of the manas; He is not the master consciousness, and does not need to take charge of anything, so He does not have so many concerns and attachments, making it easy to focus on thinking through problems, and His discernment of objects is relatively clear. The manas has many dharmas that He cognizes, is attached to, and discerns: whatever dharmas are produced by the tathāgatagarbha, the manas can reach and cognize them; all things from ancient times to the present that are related to oneself, and even the minute changes in the physical body at every instant, the manas can discern and know them all; even things unrelated to oneself, due to the habit of grasping, the manas will still attach to and worry about them. Therefore, His mental attention is not easily concentrated, His discerning wisdom is weak, and His understanding of the Dharma is not clear.

Another reason the mind consciousness's wisdom is greater than the manas's is that the mind consciousness exists for only one lifetime, is only very lightly influenced by environmental conditioning, does not have as many afflictions and ignorances as the manas, nor as many karmic obstructions, and has fewer obscurations; therefore the mind consciousness is more intelligent than the manas.

If the manas had fewer objects to cognize, if the ignorance in the mind were not very deep and heavy, and if over beginningless kalpas He had not accumulated boundless karmic obstructions of birth and death, then the manas could be as wise as the mind consciousness; even with insufficient evidence, He could still reach a reasonable conclusion and thereby realize the truth. But the manas is not like this, and that is precisely why our practice and realization are so difficult.