Who am I ?
First we must understand the principle 'I am'. 'I am' means the consciousness within your body, The 'You' that lives in your body. To understand the difference between you and your body, we will do a little experiment. Try this-Repeat the following sentences as you point to each part of your body:
"This is my head."
"This is my arm."
"This is my knee."
"This is my heart."
"This is my body."
You'll notice that each part of your body, in fact your whole body, belongs to you . You are the owner of your body. You don't day "I body." . You say "My body".
You live inside your body . But not always. At night you leave your body in your dreams. Your body is lying on your bed , but you are somewhere else in your dream body. When you wake up, you come back into your body lying on your bed. From this simple example you can begin to realize that your are actually not your body. Your are the owner of your body. You are the consciousness in your body.
According to scientific research, your body is constantly changing. You might remember your early childhood when you had a small body. Your body was very different from what you have now, but your were the same person inside your little body. AT that time you thought, "I am a child.". You identified with your little body.
Now you are grown up and you think , " I am older now." But actually your body has simply grown . Yo are the same person within the older body. You haven't changed; your body has changed; If you live so long, you'll grow old and think , "Now I'am old." . Your body will have grown old , not you. You are still the sam you, passing through changing bodies.
Who am I ?
You are the self living in your changing body.
You do not change. Your body changes.
Krishna tells in bhagavad-gita 2.13 : As the embodied soul continuously passes, in this body, from boyhood to youth to old age, the soul similarly passes into another body at death. A sober person is not bewildered by such a change.