The Principle of Silent Recitation

The manas is the consciousness that takes charge; bodily, verbal, and mental actions are all regulated and directed by the manas. The same is true of silently reciting sutras and mantras in the mind: when the manas wants to recite silently, the mind consciousness recites in the mind without making a sound. Vocal recitation is also done by the mind consciousness—it is because the manas wants to recite that the mind consciousness recites. It is also possible that the mind consciousness wants to recite, and only when the manas deems it acceptable can the mind consciousness recite. In short, in the matter of recitation, it is the manas that decides and the mind consciousness that carries it out. 

Why does the manas choose between vocal recitation and silent recitation? This choice is extremely hidden and difficult to observe. The mind consciousness always feels that it happens automatically and naturally. This feeling shows that the mind consciousness is very coarse and lacks meditative concentration, so it cannot observe the subtle and hidden aspects within. The manas makes its choice between vocal and non-vocal recitation based on the state of body and mind, based on whether the body has sufficient qi. When in meditative concentration, once the mind becomes active, one feels very tired; vocal recitation involves a greater amount of activity, and the mind consciousness feels tired, so the manas automatically chooses not to vocalize. When the body is fatigued, the manas will also choose to recite silently in the mind. On the surface it seems automatic, but in fact it is because the manas relies on the eighth consciousness and knows the state of body and mind very quickly and closely, enabling it to make choices beneficial to body and mind with great swiftness—things that many people's mind consciousness does not know about. 

Silent recitation can increase the power of meditative concentration; or, once the power of concentration has strengthened, one can no longer manage vocal recitation—vocal recitation feels mentally tiring, and so one automatically switches to silent recitation. When the power of concentration strengthens further, even silent recitation becomes tiring, and so one switches to vajra recitation, moving only the lips without making a sound, with the sound in the mind also faint. When even vajra recitation feels forced, one switches to recollection in the mind. When the power of concentration strengthens still further, even recollection is no longer possible, and one will enter deep meditative concentration, without any thoughts or mental recitation at all.