One should indeed see, hear, understand and meditate over the Self, O Maitreyi; indeed, he who has seen, heard, reflected and understood the Self – by him alone the whole world comes to be known.
Later, the doctrine of the Self was explicitated by seers like Yajnavalkya, who is up there with Plato as an ideas man next to whom a whole philosophical tradition is but a series of footnotes.
Together with Yajnavalkya, first formulator of the all-important doctrine of the Self (Atmavada), Dirghatamas was one of the key thinkers of mankind.