Sage Uddalaka sent his son Svetaketu to learn the Vedas. He returned after the required period of study. But Svetaketu was proud of his Vedic education. His father then asked him if he knew the most important thing that one had to know.
If he knew this, Uddalaka added, Svetaketu would understand everything. What was this most important thing that Uddalaka was referring to? Vaishnavite Acharya Ramanuja explained what Uddalaka meant. Uddalaka wanted his son to understand that The Supreme One was the One who commanded, V.S. Karunakarachariar said in a discourse.
In other words, Uddalaka was saying that if Svetaketu understood this fundamental fact about God, he would not be proud. Uddalaka told his son that if he understood the properties of mud, he could easily comprehend the properties of a mud pot and would know what it was worth. If he knew the properties of gold, he would understand all about gold products.
Likewise, if he understood that it was God who commanded everyone and everything in the Universe, he might be said to have understood everything.
Everything in this Universe is supported, operated and commanded by the Supreme One. The Jivatma is only one of the bodies of God. The Universe and everything in it constitutes His body. Since the Supreme One is in everyone, he was in Svetaketu too. When we point to a person and say he is so and so, it is not really a reference to the body of the person, but to the atma.
The atma in the body is like water in a container. When we ask someone to bring us a cup of water, we just say, “Can I have some water?” We make no reference to the container in which water is brought. The water which is inside is what matters. The container merely serves a certain purpose; but beyond that, it has no significance. So it is with the body. It is merely a receptacle for the atma and what matters is the atma. The atma is the body of the One who commands everything.
Lord Narayana is the Creator. Usually, the one who makes something is different from the raw material and from the finished product. But Lord Narayana is unique, for He is the raw material, the maker of the product and the final product too.