In 1969 I published in the Journal of Economic Literature a survey of recent controversies in capital theory under the same title as this book. In writing the survey I was constrained by a word limit (which, nevertheless, I managed ex post to persuade the editor to allow me to exceed by a factor of 2½) and so I often asserted rather than argued, leaving the reader to find the evidence for himself in the references that I provided. This clearly is an unsatisfactory procedure (though shortage of space is an excellent ploy with which to keep angry critics at bay); I therefore welcome the chance, which the Syndics of the Cambridge University Press have so kindly offered me, to extend the assertions into what I hope are persuasive or, at least, respectable arguments.

The plan of the book follows very closely the basic outlines of the survey. I have, however, added sections on some additional topics, most notably on the ‘dual’ to the wage-rate–rate-of-profits trade-off relationship, the maximum consumption per head–growth rate trade-off relationship in chapter 5, and have brought up to date the state of the debate in others. Of course, economics is no more immune from the knowledge explosion than any other modern discipline and anyone who attempts to write as well as to read, and who is as ill-equipped with modern techniques and memory as I am, must inevitably fall behind in the unequal race to be completely up to date.