The word I, which is just a letter, is so difficult to explain, because it cannot be seen. It cannot be heard, touched, tasted or smelt. Yet Sri Adi Sankaracharya moves from example to example in describing the I, the self, which is like the light that shines from many facets of a diamond. The description here is that the Atma or I, can know itself. It does not need another object or person to reveal itself as its very nature is knowledge.
To explain this simply, when you are just sitting, you do not need another person to tell you that you are there, sitting on the chair. “Excuse me, I know it myself,” you may probably say. You do not need any other mouthpiece to discover and say where you are. You know it because the I in you called the Atma is of the nature of knowledge. Wherever it sees, it knows and understands.
The beauty of this revelation is that it is only the shrutis that can really point this out to us. We cannot know this knowledge that we do not need anything else to point out who we are, where we are, what we are and how we are to ourselves. We simply know. How is it possible? It is possible because knowledge is our nature. It comes naturally to us to know.
The example given by Sri Adi Sankaracharya to illustrate this point is: In a dark room, there is a lamp. You need the help of the lamp to illuminate the things in the room. However you do not need another lamp to show where this lamp is present. You need not shine a torch to show the sun or the moon. In fact, when all lights go off at night and children are out playing under the night sky, they shine their torches into the darkness to see the stars and the moon, only to find out that the light is absorbed by darkness and they get to see the light only if there is an object like a tree that intercepts the light.
How does this understanding count in our daily practice? It curbs our craze to know. Knowledge makes us happy. Ignorance of anything keeps us restless. We are at peace only when we are restful. So we always set out on a search to know this and know that, to read this to study that, to learn a new musical instrument or a different genre of music, to practice some new sport. After a period of indulgence in our new passion for knowledge, the novelty wears off and we again go out searching for something new to know.
This thirst for knowledge ends only when you know that you are the one that you really need to know and that puts an end to all our efforts to know anything to be happy. By knowing your self, you know that by which everything else is known! The result of this knowledge of the self is peace.