In writing this book and preparing it for publication many have been of great help to me, some with punctilious corrections of the text, others with penetrating commentary on its content, and others again with very useful support of a practical nature. I want to express my deep appreciation to Kate Brett, Roy Clouser, Henk Geertsema, Gerben Groenewoud, Bas Jongeling, Ronald Meester, Wim van der Steen, Dick Stafleu, Tony Tol, Henk Van Andel, Nick Wolterstorff, and Uko Zylstra. This appreciation I also want to extend to Cambridge University Press for its compliant co-operation.

One name I have not yet acknowledged: namely, Harry Cook. He is Professor Emeritus of The King's University College in Edmonton Alberta, Canada. What Harry has meant for bringing this book to completion cannot easily be overstated. Some years ago, after he initially gave careful commentary on the first Dutch concept, he was prepared to translate the whole manuscript into English. Due to the large time difference between the Netherlands and Alberta, Canada, there was an intensive exchange of e-mailing which spanned day and night. Translating was for Harry the occasion to do much more: he expended a great deal of effort on this project. He is, after all, an expert on the theory and history of biology and as such he kept a close eye on the comprehensibility of the argumentation, especially for the benefit of all non-philosophical readers. He offered much bibliographical material from many sources.