India is poised to become the world’s most important country in the medium term. It has the largest population (which is still growing), and with a per capita GDP that is just one-quarter that of China’s, its economy has enormous scope for productivity gains. Moreover, India’s military and geopolitical importance will only grow, and it is a vibrant democracy whose cultural diversity will generate soft power to rival the United States and the United Kingdom.

One must credit Indian Prime Minister Narendra Modi for implementing policies that have modernised India and supported its growth. Specifically,...