V: aadmi log ka earth par kaam kya hai? (Roughly translated: What's the raison d'être i.e. purpose of man on earth)? "kaam" has several shades of meaning for him. But, that's what I think he meant.) 
Me: What's the purpose of plants on earth? 
V: hmm.. nothing 
Me: What's the purpose of animals, like a tiger, a deer or a cow? 
V: hmm.. just live 
Me: Man is also an animal. Same for man. 
V: so there is no purpose...? 
Me: So, there is no purpose. But, yes, since we are born already, we might as well live and enjoy the life on earth. And while enjoying, not harm others so they can also enjoy and also leave the planet sensibly, just like others left it for us. 
V: (moves away, deep in thought.)  

I think that pretty much sums up my philosophy of life 😄