Those who are in this world experience hunger and thirst. But the Vaishnavite saint Nammazhvar, although he had an earthly sojourn, knew no hunger or thirst. Those in Sri Vaikuntha are the ones who do not experience the pangs of hunger or thirst. But those in Sri Vaikuntha do not come down to Earth. Nammazhvar might have lived in this world, but he had the experience of those in Sri Vaikuntha. All the Azhvars came for a purpose. They were sent by Lord Narayana, so that we too may see that service to Lord Narayana is the only thing we should aspire for. The Azhvars were easily able to see His supremacy in the idol forms too, said Adur Asuri Madhavachari. Our enjoyment of the idol form can never be on a par with theirs, because of our karmas.
What is most difficult for human beings to have? Bhakti is what is beyond our reach. The reason lies in our ignorance. As long as we see the body and the soul as one and the same, we can never get anywhere near the path of bhakti. Will flowers bloom in the heat of a blacksmith's forge? Will water be available in a desert? As impossible as these is it to see bhakti in this world. It was in such a world that Nammazhvar lived, but with no thoughts of anything but Lord Narayana.
The essence of the Sastras is that everything that is sentient and non-sentient constitutes the body of the Lord, and that Lord Narayana is the Soul. The body exists only because of the Soul and is controlled by it. The body exists only for the pleasure of the Soul. In other words, Lord Narayana is the Soul and everything else constitutes the body. Lord Narayana is the One for whose pleasure the jivatmas exist. The nature of the jivatma is such that it must perform service to the Divine Couple. And the only way to do that is to aspire for moksha. And the only way to get moksha is through bhakti or surrender. All other activities such as bathing in sacred rivers etc., must lead to bhakti or surrender. They cannot by themselves give us moksha. Without bhakti or surrender, there can be no moksha.
These truths are there in the Sastras. But Nammazhvar gave us these truths in Tamil.