Introductory perspectives Ever since Marx proposed his “law of the falling tendency of the rate of profit” – in Capital, Vol. III, Part 3, based on the 1865 manuscripts completed before Vol. I was published, and therefore not chosen for inclusion in that volume – a huge debate has raged. This is, in Marx’s own words, “the most important law of modern political economy,” and yet it is surrounded by qualification, in the form of “counteracting forces” whose range of action remains unclear. Did Marx succeed in establishing that the tendency would prevail, in reasonably finite time, over its countertendencies? Most generally, in our continuing development and reconstruction of Marxist political economy, how should the crucial matter of secular crisis – long-term structural transformation that progressively undermines and problematizes systemic reproduction – be understood?