According to Indian philosophy it is Prana, the life force or vital force, that keeps the body functional. The Chandogya Upanishad underscores this point through a charming allegory that is used for the purpose of meditation on Prana: the ‘Oldest and Greatest’.
A dispute once arose among the sensory organs as to who was superior. Finding no solution, they repaired to their father Prajapati (the lord of creatures) to settle the dispute. ‘He is the greatest among you on whose departure the body appears to be most despicable’, replied Prajapati.
Speech was the first to leave its abode in the body and go into voluntary exile for a year. On return, it enquired how the others had managed in its absence. The other organs replied: ‘Just as the dumb, without speaking; living with the help of Prana, seeing through the eye, hearing with the ear, thinking with the mind.’ Speech re-entered the body disappointed.
Next the eye and the ear left in succession. They too were disappointed to discover that except for blindness and deafness the body was all right. Then the mind went out. When it returned and made anxious enquiries, the sense organs chorused, ‘We lived as children with unformed minds do, without thinking — living with the help of Prana, speaking with the tongue, seeing through the eye, hearing with the ear.’ Dejected, the mind re-entered too.
Now it was Prana’s turn to leave. As it proceeded to depart, it ‘pulled out the other organs as a spirited horse pulls out the pegs to which its legs have been tied’. It didn’t require further persuasion to decide the winner. The sense organs and mind united in prayer to Prana: ‘Be our ruler, you are the greatest, please do not depart.’