Ordinarily, we think the circumstances in a dream are not real while experiences during the day are real. If we perceive the world outside to be truly existent, i.e., real and not illusory, this belief in true existence is called “self.” In the Middle Way doctrine, the “self” is clearly defined as a distinct and permanent entity which exists in its own right and does not depend on other things to come into being.

- Quote from The Four Seals of Dhama, "All Phenomena Lack Self-Existence"