The Shiv Sena?s latest attempt to stir up sentiment in favour of ?Mumbai for Marathis? has stirred up many predictable reactions as well as a few surprises. Some have suggested that the repudiation of the Sena?s call by the BJP and RSS represents the first real sign of the BJP?s transformation into a more representative party of the right. As desirable as this would be, such speculation seems unwarranted for now: the BJP is merely doing what any smart party with national aspirations would do in the face of an embarrassing factional squabble between two local parties with a more parochial voter base.

The strong outrage in Mumbai and elsewhere in India over the suggestion that migration from north India should be stopped was as predictable as it was right. Mumbai is an Indian city: its prosperity has depended on labour from UP and Bihar (as well as from the Konkan) for more than 150 years, and what happens in Mumbai usually reflects and affects what happens in the rest of the country. No political programme aimed at ensuring the city?s prosperity could ever seriously suggest sealing the city off from one of its most important labour hinterlands, and Mumbai?s very nature means that it can never go back to being just a regional capital.

Tensions over language are not new to Mumbai?and they are never easy to resolve. Europe spent much of the first half of the twentieth century trying to make national borders coincide with languages, and it only sort of succeeded after two destructive wars and a series of tragic expulsions of whole populations in 1945. But just as Europe?s wars were about more than just language, this latest fuss over the Marathi manoos and his language is about something else too: the tension between Mumbai?s aspiration to become a city with a major global footprint and the increasing competition at present for jobs, space and resources.

Mumbai is already one of the biggest cities in the world in terms of population, and sooner or later it will have to decide if it wants to become one of the greatest. History and economics tell us that prosperous cities share a small number of key features: diversity, openness in attracting talent, and the density and speed to turn innovations into new companies, products and industries. These factors explain why London and New York prosper during boom years and weather the downturns, while cities like Tokyo stall permanently if the economic cycle turns against them. Mumbai already has diversity, openness and density, but it still lacks the high quality infrastructure and easy access to capital that would make innovation and creativity really matter. Finding ways to make a growing Mumbai liveable and prosperous is the right answer; keeping migrants out is not.

The Sena does have one thing right, even if it is proposing the wrong solution. Locals inevitably resent migrants if they have to compete with them for scarce jobs, housing and other resources?and the division becomes even more fraught if language is involved as well. The fractures and tensions that eventually led to Karachi?s murderous ethnic violence are one illustration of what can happen if language or ethnicity becomes the proxy for grievances over resources or perceived deprivation. The worst outcome for Mumbai would be one in which linguistic solitudes were reinforced by economic divides.

Mumbai is not about to become Karachi?or, for that matter, an exclusive colony for the sons of Maharashtra?s soil. Mumbaikars have resisted attempts to provoke religious tensions in the city over the past two decades, and the city?s strong neighbourhoods will not easily fall prey to violence over language or regional origins. Nor can Mumbai put up barriers and stop growing. Its politicians need to look for new ways to mobilise resources and create infrastructure instead of trying to keep new arrivals out.

The most important thing Mumbai?s politicians can do is to learn the difference between language and belonging. Everyone who chooses to live in Mumbai belongs to the city, whatever his native language or native place. Punishment or persecution will not teach Mumbaikars to communicate in Marathi: only shared prosperity, a good education system and a strong sense of belonging can do that.

The author has taught Indian history at Oxford and Cambridge Universities