`But when his speech is merged in his mind, his mind in breath, breath in heat (fire), heat in the Highest Being, then he knows them not. `That which is the subtile essence, in it all that exists has its self. It is the True. It is the Self, and thou, O Svetaketu, art it.' `Please, Sir, inform me still more,' said the son. `Be it so, my child,' the father replied.