In plain words
We put a little sugar into water. When we stir it well, all that sugar spreads through the water, everywhere. But the eye cannot see it. The hand cannot grasp it. But is the sugar not there? It is there. It is there without form. It is there beyond reach. But only through the tongue, and the tongue alone, can we recognise that it is there. When we recognise it, what does the sugar say? Tat tvam asi. That sweetness, too, is not the water's, that sweetness. In this way the great ṛṣis of that age taught and spread, through little sentences like these, the truth that God is present everywhere, and went on teaching the oneness called Tat tvam asi.
Not only this, man makes no fitting effort to recognise his own true nature, his own life and the world around him. What is, is one alone, and it goes on taking form as the many. The Upaniṣads also went on proclaiming that the oneness in the many is the power of Bhāratīya culture. Forgetting the oneness and putting our faith in the many, we are wasting our lives.
Here, the one form of these three, the letter A, the letter U and the letter M, is Oṃkāra. The measure of this Oṃkāra in sound is the Praṇava. This Praṇava itself is the form of the world. So this world is the great form of Oṃkāra itself. These two, too, are ever being sent out, from heaven to earth and from earth to heaven. The Upaniṣad went on teaching that to recognise the principle of the Ātma within the oneness of these two is true manliness. The reason? In every human being this sound of the Praṇava is filled in a silent form. We may wonder: "We do not see the Praṇava anywhere, we do not hear it!" What is our breathing in and breathing out? What is the flow of the blood that moves through our body? All these are full of the Praṇava. The wind blows through the trees. In that wind, too, the sound of the Praṇava is heard. If you go to an electric pole, stand there and put your ear to that electric pole, we can hear that sound, Om. But because we merely imagine some invented things on this Praṇava, we do not recognise that it takes the form of the Praṇava. In our daily life we breathe in and breathe out. When we breathe in, we draw the air with So…