According to Master Shengyen, “While you are practicing just sitting, be clear about everything going on in your mind. Whatever you feel, be aware of it, but never abandon the awareness of your whole body sitting there. Shikantaza is not sitting with nothing to do; it is a very demanding practice, requiring diligence as well as alertness. If your practice goes well, you will experience the ‘dropping off’ of sensations and thoughts. You need to stay with it and begin to take the whole environment as your body. Whatever enters the door of your senses becomes one totality, extending from your body to the whole environment. This is silent illumination.
Hakuun Ryōko Yasutani says: “Shikantaza is the mind of someone facing death. Let us imagine that you are engaged in a duel of swordsmanship of the kind that used to take place in ancient Japan. As you face your opponent you are unceasingly watchful, set, ready. Were you to relax your vigilance even momentarily, you would be cut down instantly. A crowd gathers to see the fight. Since you are not blind you see them from the corner of your eye, and since you are not deaf you hear them. But not for an instant is your mind captured by these impressions.”