Whether you’re building a business or a cathedral, execution is everything. We ask artists, scientists, and inventors how they turned ideas into reality. And we find out why it’s so hard for a group to get things done — and what you can do about it. (Ep. 4 of the “How to Be Creative” series.)

In 2005, Raghuram Rajan said the financial system was at risk “of a catastrophic meltdown.” After stints at the I.M.F. and India’s central bank, he sees another potential crisis — and he offers a solution. Is it stronger governments? Freer markets? Rajan’s answer: neither.