A koan (known in Chinese as a gong an, and in Vietnamese as a cong an) is a meditation device, a special kind of Zen riddle. Koans are solved not with the intellect but with the practice of mindfulness, concentration and insight. A koan can be contemplated and practiced individually or collectively, but so long as it remains unsolved, a koan is unsettling. It is like an arrow piercing our body which we cannot take out; so long as it is lodged there we can neither be happy nor at peace.

Though you may not fully know whether the teachers of the various localities are wrong or right, if your own basis is solid and genuine, the poisons of wrong doctrines will not be able to harm you, "keeping the mind still" and "forgetting concerns" included. If you always "forget concerns" and "keep the mind still,"

Zazen is a particular kind of meditation, unique to Zen, that functions centrally as the very heart of the practice. In fact, Zen Buddhists are generally known as the "meditation Buddhists." Basically, zazen is the study of the self.

When meditating, is it necessary to focus on one specific object? This is not always necessary, but at times it can be very helpful. When you do meditate on a specific object, such as the breath, that object will help you to develop concentration, and concentration will enable you to cultivate a quiet and spacious mind.