It is no longer necessary for an economist to apologize when introducing the subject of technological change. That is, in itself, a (modest) cause for celebration, since the situation was very different as recently as forty years ago. At that time, economics had still not been awakened from its dogmatic slumber on the subject, and was content to treat – or perhaps a more appropriate operational verb would be “to dismiss” – technological change purely as an exogenous variable, one that had economic consequences but no visible economic antecedents. Although sympathetic readers of Marx and Schumpeter had learned to attach great importance to technological change as a major impulse – perhaps the major impulse – in generating longterm economic growth, such an awareness had not yet rubbed off on the dominant academic traditions of western economics.

Today, the economic importance of technological change is widely acknowledged. There cannot be many economists who would dissent from the view that the growth of technological knowledge is fundamental to the improvement of economic performance. In addition, it is widely accepted that, in advanced industrial economies, the growth in technological knowledge relies increasingly, although in ways that are never clearly specified, on science.

Thus, it seems reasonable to pose two questions: what can be said about the manner in which the stock of technological knowledge grows over time? And, to what factors is it responsive, and in what ways?

In dealing with these questions I will argue that the main features of the stock of technological knowledge available at any given time can only be understood by a systematic examination of the earlier history out of which it emerged.