New Delhi, Sept. 15 -- As India concludes its Brics summit and prepares to hand the baton to China, the grouping finds itself at an important inflexion point. Its first decade was largely about giving the Global South a stronger voice. The next should be about turning that voice into capital, investment and development.

The New Delhi Declaration points in that direction. Beneath the geopolitical language is a more interesting story: Brics is gradually assembling pieces of a financial architecture around local-currency finance, payment interoperability, guarantees, a stronger New Development Bank (NDB), climate finance, and private investment.

The test now is whether these pieces can actually change how capital flows into emerging market...