Another example how Thomas Piketty's book Capital in the 21st Century, which has achieved mainstream popularity, is unhinging orthodox economics can be found in Greg Mankiw's recent NYT's column "How inherited wealth helps the economy." First there is this, which concerns Piketty's fairly bland predication that, under the current state of things (low taxes for the rich), inequality will grow in the coming years:

[G]iven economists’ abysmal track record in forecasting, especially over long time horizons, any such prognostication should be taken with a shaker or two of salt. The Piketty scenario is best viewed not as a solid prediction but as a provocative speculation.
Why is this a stunningly stupid statement? Until the Crash of 2008, orthodox economists bragged nonstop about having the future down and taming the business cycle. Their confidence was such that they named this achievement, this emasculation of the future, this unbelievable power to manage risk, the Great Moderation. Also, some economists were so impressed with their command of risks (meaning the future) that they believed a crash like the one in 2008 could only happen 3 or so times in the history of the universe—which, by the way, has been around for 13.8 billion years. Now all of a sudden economists can not predict the future. Now all of a sudden it is best to be cautious.

Then there is this:

Because capital is subject to diminishing returns, an increase in its supply causes each unit of capital to earn less. And because increased capital raises labor productivity, workers enjoy higher wages. In other words, by saving rather than spending, those who leave an estate to their heirs induce an unintended redistribution of income from other owners of capital toward workers.

The bottom line is that inherited wealth is not an economic threat. Those who have earned extraordinary incomes naturally want to share their good fortune with their descendants. Those of us not lucky enough to be born into one of these families benefit as well, as their accumulation of capital raises our productivity, wages and living standards.

I must remind you that this is an economics professor at Harvard, one of the most prestigious "centers of learning" in the world, and what he is arguing in a prestigious newspaper, The New York Times, is that the capital rich people save for their untalented children ("intergenerational altruism"—meaning, money is amassed by way of talent and genius; meaning, the private ownership of monstrous sums of money is justified) will in the end benefit labor. This is simply astonishing. And this is based on the diminishing returns on capital, something that many Marxist theorists and also heterodox economists like Andrew Glyn (they call it the "profit squeeze") have correctly seen as one of the leading reasons for the rise of neoliberalism in the mid-70s and the attack on labor in the early 80s (to revive profits). But here it has beneficial consequences for working men and women. The capital saved by the rich returns to those at the bottom because it provides the economy with the extra capital that's needed to counter diminishing returns on earlier capital investments. Worse still, the Harvard professor really believes saved capital provides money for business investments and not debt provided ex nihilo by banks. Also, he seems to have no idea that much of saved capital of this kind ends up in the equity markets, which have very little to do with creating new businesses but instead extracting rent from current ones (shareholder value). What insanity. And a professor at Harvard.