What is the underlying theme of the novel explained by Mr. Panwallah from TVBTS?

Depending upon the text in question, we might consider a few different themes. One theme is the way in which the wheel of time keeps turning regardless of whether or not people want it to. Factories will be built. Jobs will be gained and lost. Former modes of working and living will fade away and others will take their places. Change and adaptation are not easily done, especially by older generations, but they are often what is necessary to keep going. Whereas someone like Sayyid Ali deplores change, Mr. Panwallah embraces it. Hari respects both of these men but ultimately adopts Mr. Panwallah's perspective because it is what he has to do to survive, and what he has to do to find meaning in life and respect for himself.

In addition, there is also the theme of "kindness to strangers". Desai accurately paints a picture of how lonely, confusing, and destabilizing the city can be, especially to a young boy from the rural seaside. He knows no one would be able to survive if it were not for the kindness of Hira Lal, Jagu, and Mr. Panwallah. These individuals have no obligation to Hari but see in him a struggling child who needs guidance. Through them he gains a job, money, a place to stay, and, thanks to Mr. Panwallah, an actual future and the kind of confidence that will help bring that future about.