Seokmun Hoheup is one's Brightness. This Brightness is Light, and the Light is the path(도/道/Do) that guides one toward Their Essential Self. Through the publication of this book on Seokmun Hoheup, I present the 15-level practice process to all those who, even at this very moment, devote themselves with wholehearted passion to the journey of self-inquiry, asking the timeless question: "Who am I?" I sincerely hope that many will find Their Essential Selves through the practice of Seokmun Hoheup.