The Second Machine Age

Definition

Human history, plotted as population and social development over time, is a nearly flat line for millennia until the late eighteenth century, when it bends almost vertical. That bend was the Industrial Revolution, driven by the steam engine's ability to generate mechanical power beyond the limits of human and animal muscle — the first machine age. The second machine age is the claim that computers and digital technology are now doing the analogous thing for mental power: "the ability to use our brains to understand and shape our environments."

In the Book

Brynjolfsson and McAfee open with historian Ian Morris's graph of "social development" across 25,000 years, showing that agriculture, empires, religions, and writing barely dent the curve — only the steam engine, refined by James Watt between 1765 and 1776, bends it. They use this to set up their central analogy: just as the steam engine's descendants overcame the limitations of physical power and produced factories, mass production, and modern life, digital technology is now overcoming the limitations of mental power. The book's three-part structure follows from this frame — part one (chapters 1–6) establishes why digital progress is accelerating now, part two (chapters 7–11) traces its economic consequences ("bounty" and "spread"), and part three (chapters 12–15) asks what should be done about it.

Why It Matters

Naming an era as a second instance of a known pattern lets you import everything already learned about the first instance — including its decades of disruption, its need for new institutions, and the fact that its benefits were not automatic or evenly distributed. The move is domain-general: any time a new capability threatens to remove a long-standing constraint (on labor, on distance, on memory, on attention), asking "what did the last time this happened look like, and what took decades to catch up" is a way to forecast the adjustment costs, not just the upside.