Capitalism in the 21st Century (Piketty 2014) made a big splash recently by calling attention to the probability that the growing inequality of wealth was unlikely to diminish in the future. The central thesis rests on the slow economic growth rates increasing the capacity of those with wealth to gain more than the growth rate from their investments. With little economic growth, not much remains to distribute to workers and middle management.His analysis gives little consideration to the role of knowledge growth, including technology, in explaining social inequality simply because his data over the longue durée of two and half centuries quite correctly downplays its importance. But since the third stage, knowledge creation increasingly dominates the shape of the stratification system. It might be noted, however, that Piketty (2014) has less interest in this problem and more in what the 1 percent gain across time and whether their wealth is generated by inheritance or income. By focusing on how knowledge shapes the stratification system, his view of social inequality can be integrated into the discussion of Marx and Engels's theory of capitalism (Feuer 1959: chapter 1) as well as research work of the past 50 years.

Why bother with Marx and Engels (Feuer 1959: chapter 1), now more than a century and half later? The first and most critical reason remains that they focused on the shape of the stratification system and how it transforms across time. In addition, they have left a legacy in American sociology (Manza and McCarthy 2011) because of their emphasis on machines and unemployment. Since some of its most famous predictions such as increasing economic crises leading to a socialist revolution have not come to pass, many have rejected their thinking. Yet, at the same time, some of the same competitive processes generating economic crises apply today and are well described by their theory as we have seen in the rise of the rust- belt communities and other pockets of poverty discussed in Chapter Two. Beyond this, there has been a recent resurgence of interest in critical theory, one of the major contributions from the Marxist perspective (Thompson 2016). When various parts of a theory appear to be still relevant in explaining social processes, it seems more reasonable to update the theory and in particular retain those hypotheses that have supporting evidence.