The teaching of the Three Doors of Liberation is common to all the Buddhist schools. The first door is emptiness. Everything is empty. Empty of what? Empty of a separate self. A flower is full of everything in the cosmos—sunshine, clouds, air, and space. It is empty of only one thing, a separate existence. That is the meaning of emptiness. We can use this as a key to unlock the door to reality. The second door is signlessness. If you see a flower only as a flower and don’t see the sunshine, clouds, earth, time, and space in it, you are caught in the sign of the flower. But when you have touched the nature of interbeing of the flower, you truly see the flower. If you see a person and don’t also see his society, education, ancestors, culture, and environment, you have not really seen that person. Instead, you have been taken in by the sign of that person, the outward appearance of a separate self. When you can see that person deeply, you touch the whole cosmos and you will not be fooled by appearances. This is called signlessness. The third door is aimlessness. We already are what we want to become. We don’t have to become someone else. All we have to do is be ourselves, fully and authentically. We don’t have to run after anything. We already contain the whole cosmos. We simply return to ourselves through mindfulness and touch the peace and joy that are already present within us and all around us. I have arrived. I am already home. There is nothing to do. This is the third key for unlocking reality. Aimlessness, non-attainment, is a wonderful practice.
– The Pocket Thich Nhat Hanh (Shambhala Pocket Classics)