Shallow Samādhi and Deep Samādhi

Question: In meditation, I found that when the mind attends to a subjectively imagined realm, the meditative concentration (samādhi) is deeper than when it attends to the five sense objects. What is the reason for this? 

Answer: When attending to the five sense objects, the six consciousnesses are all active: the eye consciousness wants to see, the ear consciousness wants to hear, the nose consciousness wants to smell, the tongue consciousness wants to taste, the body consciousness wants to touch, and the mind consciousness wants to know. With such bustle and confusion, it is naturally not easy to attain meditative concentration, and even if there is concentration, it is shallow concentration. But once the five consciousnesses are sealed off and bound, only the perception of the solitary consciousness (mano-vijñāna-eka-citta) remains, which can discern and know more concentratedly, so of course it is easier to enter concentration; and once concentration is entered, the concentration can be relatively deep. When the solitary consciousness is also restricted, the concentration becomes even deeper. The fewer consciousnesses participating in discernment, the deeper the concentration; the fewer objects discerned, the deeper the concentration. Therefore, in the deepest cessation (nirodha-samāpatti), there is no discernment by the six consciousnesses—only the manas alone carries on a relatively slight discernment. When the power of concentration is insufficient and very shallow, do not engage in contemplative practice (vipaśyanā-caryā); as soon as you contemplate, you become scattered. When contemplation cannot be carried out, single-mindedly cultivate concentration and refrain from contemplating for the time being. When the power of concentration is somewhat deeper, then contemplate, and the results will be better. The methods of practice should be grasped and applied flexibly, treating each specific situation on its own merits; one must not generalize.