There are some economic problems for which historical analysis is especially well suited, indeed essential. Economic historians who fail to be motivated by this fact are doomed to have only the most limited and transitory impact on economic thought. Paul David is one of our best pathfinders in this entwined thicket of theory and history. The appearance of his book Technical Choice, Innovation and Economic Growth (1975) should help speed the diffusion of some highly original ideas on technological change, distribution, and economic growth. David is an economic historian or better, an economist and a historian who hammers on the toughest theoretical nuts and who recognizes the true value of history in shedding light on economic dynamics. The book is separated into two parts. A very long chapter 1 deals with technical choice, innovation, and technological change at very high levels of aggregation. Here David writes macrohistory in the grand style and emerges grasping an aggregate model of growth with the bias and the rate of technological change endogenous. If it held water, it would be an achievement of some note. I have doubts, and they are presented at the end of this review in Section IV. They appear last in the review since they reflect on Professor David's thoughts of most recent vintage. The majority of the book's pages, however, are devoted to "microhistorical" essays published between 1966 and 1973, two of which have already become classics. Chapters 2 and 3 deal with learning by doing as an endogenous source of efficiency improvement.' Section II will