Too many politicians seem to reach for 'infrastructure' as the default answer to investment, as if roads and bridges were the answer to everything. Even the IMF and the World Bank seem to mainly offer infrastructure spending as an alternative to austerity, although they are right to focus on the need for investment.

Our current model of capitalism and the dominant ideas in policy making have led to a failure of investment by both the public and the private sector in the things that drive productivity, and which affect its distribution.

While infrastructure is of course important, it must be part of a bigger vision. The point is not to simply dig ditches but to steer those investments towards transformational growth.

If we look at Germany's infrastructure policy, it has been driven by its mission-oriented focus on green infrastructure. This affects both innovation and infrastructure, old industries and new. The German steel industry, for example, has adapted to the policy by lowering its material content through a 'repurpose, reuse and recycle' strategy.

There is a lot of flesh to be put on the bones - but there is at least an opening for a more pragmatic, less ideological debate about how to build economies that work for people, within the limits of our planet.

An interesting attribute of public banks is that they don't only de-risk the downside, but also get a share of the upside.

Markets are not static entities that are 'intervened' in (for good or bad) but are outcomes of public and private interactions.