As you sing, read the songs of Narottama Dasa Thakura all the teachings of the Vedas are there. So they have access to Vedas and all the sastras and we just get a little glimpse of what he is trying to convey, more or less depending upon how much surrendered souls we are,  how much purified souls we are, to that degree we understand that song of Narottama Dasa Thakura.