I began writing this book about twelve years ago, after finally abandoning the revision of my doctoral dissertation and deciding to instead start anew and write a fresh account of the Cartesian metaphysics. I had basically finished what you now have in your hands by 1994. At that point I still thought that it would contain a fourth part exploring the origins and development of idealism. However, I have recently come to realize that the present essay is complete as it stands and that that final part is in fact an independent project which will see the light in its own time.

In writing this essay I have incurred many debts, too many to recall and properly acknowledge here. I beg the forgiveness of those institutions or persons to whom I am obliged but whom I have failed to mention.

Some of the research which I did in the early eighties has found its way into this essay particularly in chapters 7 and 8. I thank the generosity and kindness of the Master and Fellows of St John's College, Cambridge for the opportunity to carry it out in a most congenial and intellectually stimulating environment. Some sections of chapter 5 were written in one of the most beautiful urban settings in the world while on a visiting appointment at the University of British Columbia in the autumn of 1991; I thank the Philosophy Department there, and especially Paul Russell, for that opportunity.