KATHOPNISHAD CHAPTER 4 SHLOK 4

                                                          स्वप्नान्तं जागरितान्तं 

                                                          चोभौयेनानुपश्यति । 

                                                          महान्तं विभुमात्मानं 

                                                        मत्वा धीरोन शोचति ॥ ४

                                               SWAPNATAM JAGARITANTAM

                                        CHA UBHAU YENA ANUPASHYANTI |

                                          MAHANTAM VIBHUM ATMANAM

                                              MATVA DHIRO NA SOCHATI ||4

    BY WHICH- AT THE END OF DREAM AND AT THE END OF WAKING ,WE PERCEIVE

                           -THAT ATMAN IS GREAT AND OMNIPRESENT -

                      -HAVING KNOWN THIS THE WISE DO OT GRIEVE ||4

    In many and may be all the scriptures there is repetition. But we need that . It is like putting a nail in the wall Just one stroke of hammer is not enough but we need to strike it several times till the nail is deep enough and would not come out easily. The principle is same . When we are told the same thing in many different ways or by many different examples we will have the knowledge deep rooted such that it will or be displaced. So in this Shlok we are told that it not only when we are awake that we perceive due to the Atman but also in dream state we perceive due to Atman -the self. So in the Shlok before this one we were told that all that we perceive with our sense organs, is due to the Atman . That was about our waking state . When we are awake we see, touch , smell  taste hear - all the things that we do or think we DO with our senses, is due to Atman or the self . In this one Yama is stating that it is not limited to just related to when we are awake, but also when we are asleep and have dream, all the things that are perceived are due to Atman or self. This can be explained by taking an example of computer . The computer has all sorts of data  and information stored  and we als can access web and get more information. But without the electricity we can not run the computer  and we can not get anything out of it . So the web is like our sense organs . With the use of sense organs we get information of the out side world. With the help of web, we get information . But that will not be possible if the electricity that is required for running computer is not there . The same with the information that is stored in computer . We may have lots of information stored in our brain computer . But if we don't have Atman we can  not access it - same as we can not access the information stored in computer can not be accessed if we do not have electricity .   

   So in this Shlok Lord of Death is telling Nachiket that Atman is required to have experiences of wake and dream state . Once on realizes this truth then one does not grieve -of death of physical body  and along with that the sense organs as the the ATMAN or the SELF does not die .The wise or enlightened one will not grieve the death of physical body.