What is the Buddha Smile? There are two kinds of awareness: the primary Awareness AS and the secondary Awareness OF. The primary awareness is always on, but the secondary awareness like a flashlight must look around for something to be Aware Of. When Awareness OF lands on something—and in our culture when it is always on something inside or out, the subject also arises. Our language dictates that reality is a subject-object relationship.
But in our primary Awareness AS, there is no subject, just a 360 degree non-focused awareness or gestalt. Awareness OF is then Aware Of Awareness AS. Zen Buddhism is primarily concerned with awakening Awareness AS, our primary awareness out of which Awareness OF evolved. This Awareness AS is the Buddha Smile, or our Buddha Nature. (I thank Albert Low, Zen master for the conceptual language in order to talk about this).
When we drop into Awareness AS we experience unity consciousness with reality. It’s called samadhi. We are always already in Unity Awareness or Awareness AS, but our culture only recognize Awareness OF as consciousness, so Awareness AS has become a threat to Awareness OF because there is no self there. In Zen it is No-Mind.