With the world's industrial democracies in crisis, two competing narratives of its sources - and appropriate remedies - are emerging.
The first, better-known diagnosis is that demand has collapsed because of high debt accumulated before the crisis. Households - and countries - that were most prone to spend cannot borrow any more.
To revive growth, others must be encouraged to spend - governments that can still borrow should run larger deficits, and rock-bottom interest rates should discourage thrifty households from saving.
Under these circumstances, budgetary recklessness is a virtue, at least in the short term. In the medium term, once growth revives, debt can be reduced and the financial sector curbed so that it does not inflict another crisis on the world.
This narrative - the standard Keynesian line, modified for a debt crisis - is the one to which many governments, central banks and economists have subscribed. It needs little elaboration. Its virtue is that it gives policymakers something clear to do. Unfortunately, despite past stimulus, growth is still tepid, and it is increasingly difficult to find sensible new spending that can pay off in the short run.
Attention is therefore shifting to the second narrative, which suggests that the advanced economies' fundamental capacity to grow by making useful things has been declining for decades, a trend that was masked by debt-fuelled spending.
More such spending will not return these countries to sustainable growth. Instead, they must improve the environment for growth.
The second narrative starts with the 1950s and 1960s, an era of rapid growth in the West and Japan.
Several factors - including postwar reconstruction, the resurgence of trade after the protectionist 1930s, the introduction of new technologies in power, transport and communications across countries, and expansion of educational attainment - underpinned the long boom.
But, as Tyler Cowen has argued in his book The Great Stagnation, once these "low-hanging fruit" were plucked, it became much harder to propel growth from the 1970s onwards.
Meanwhile, as Wolfgang Streeck writes persuasively in New Left Review, democratic governments, facing what seemed, in the 1960s, to be an endless vista of innovation and growth, were quick to expand the welfare state. But, when growth faltered, this meant that government spending expanded, even as state resources shrank. For a while, central banks accommodated that spending. The resulting high inflation created widespread discontent, especially because little growth resulted. Faith in Keynesian stimulus diminished, though high inflation did reduce public-debt levels.
Central banks then began to focus on low and stable inflation as their primary objective, and became more independent of their political masters.
However, deficit spending by governments continued apace, and public debt as a share of GDP in industrial countries climbed steadily from the late 1970s, this time without inflation to reduce its real value.
Recognising the need to find new sources of growth, the US in the 1980s deregulated industry and the financial sector, as did Britain. Productivity growth increased substantially in these countries over time, which persuaded continental Europe to do likewise.
Yet this growth was not enough, given previous governments' generous promises of health care and pensions - promises made even less tenable by rising life expectancy and falling birth rates. Public debt continued to grow. And the incomes of the moderately educated middle class failed to benefit from deregulation-led growth - although it improved their lot as consumers.
The most recent phase of the advanced economies' frenzied search for growth took different forms. In some countries, most notable among them the US, a private-sector credit boom created jobs in low-skill industries and precipitated a consumption boom as people borrowed against overvalued homes. In other countries, a government-led hiring spree created secure jobs for the moderately educated.
Three powerful forces, one hopes, will help to create more productive jobs: better use of information and communications technology (and new ways to make it pay), lower-cost energy as alternative sources are harnessed, and sharply rising demand in emerging markets for higher-value-added goods.
The advanced countries have a choice. They can act as if all is well, or they can treat the crisis as a wake-up call to fix what debt has papered over in the past few decades.
For better or worse, the narrative that persuades these countries' governments and publics will determine their future - and that of the global economy.
Raghuram Rajan is a professor of finance at the Booth School of Business in Chicago and the author of Fault Lines: How Hidden Fractures Still Threaten the World Economy
* Project Syndicate