As a teenager growing up in the late thirties in New York, I became sceptical about a lot of ideologies then being discussed. It was only when I went to college at Columbia in the early 1940s that I became acquainted with the actual arguments of the Greek sceptics. I was a student in the course of the history of philosophy, then being given by John Herman Randall. The materials we were asked to read by Plato and Aristotle were very tough going for me at the time. After that we were assigned to read a section of the writings of the Greek sceptic Sextus Empiricus. I remember taking the book off the shelf in the philosophy library and finding it amazingly lucid and exciting. I read it on the subway ride back to my home in the Bronx and read it with much joy in the days thereafter. This text, plus the later readings from the Scottish sceptic David Hume, were the most interesting for me. In 1944 I took a seminar in post-Aristotelian Greek philosophy, given by Paul Oskar Kristeller. This was, in fact, the first course he gave in the United States. There were just two students attending. He would lecture from a podium for an hour and a half and then say, “Are there any questions, gentlemen?” Of the fifteen weeks of the course, two were devoted to Sextus Empiricus. This greatly increased my interest in Greek scepticism. When I asked Professor Kristeller years later why he devoted so much time to Sextus, whose ideas he did not find congenial, he told me that he was then following the notes from a course that his teacher, Martin Heidegger, had given!
In the next couple of years, I wrote term papers comparing Sextus with all sorts of people and using his arguments with regard to all sorts of problems. When I was at Yale in 1946 I wrote a term paper for a seminar on Hume about Hume and Sextus Empiricus, in which I tried to show that Hume’s best arguments are modified forms of arguments in Sextus. When I showed this paper to Professor Kristeller, he told me that he found it very interesting and that I should look into whether there was a sceptical tradition in Europe before Hume. This led me into reading Pierre Bayle, Montaigne, and other figures of the sixteenth and seventeenth centuries.
The thesis of this book started to develop around 1950, when I had just finished my doctorate and was beginning to do new research. At the time I was very interested in similarities I found in the arguments of David Hume and the Irish philosopher George Berkeley with those of ancient Greek sceptics. After publishing studies on this, I began to formulate my view that modern philosophy developed out of a sceptical crisis that challenged all previous knowledge, a crisis that developed in the sixteenth century. I published a long article on this in 1953–54 in the Review of Metaphysics. The long article was originally a talk I gave to the Humanities Society at the University of Iowa. I sent it to my former teacher, Paul Weiss, who was then editor of the New Review of Metaphysics. He said he would be happy to publish it if I would footnote every name and title mentioned. This resulted in an exceedingly long three-part article. Thanks to a Fulbright fellowship in 1952–53 I was able to rummage into the writings of various sceptical thinkers from the sixteenth century on. This led me to see that the sceptical crisis was in part a reaction to the clash of religious positions during the Reformation and Counter-Reformation. Over the next few years, I wrote many studies on different sceptics from Erasmus onward. After another year in Europe in 1957–58 at the University of Utrecht, I completed a book-length manuscript, putting together my findings under the title The History of Scepticism from Erasmus to Descartes. The book was submitted to two major academic presses in the United States, which both turned it down on the grounds that it was not sufficiently philosophical. It was then published by the University of Utrecht in 1960. Much to my surprise, it was quickly accepted by scholars in Europe and America. A paperback edition for course use was put out by Harper and Row in 1964.
Originally I had planned to continue the story of the impact of scepticism on modern philosophy in a series of volumes dealing with the period after Descartes. I had outlined such a series carrying the story up to the early nineteenth century. Because of other concerns, I delayed doing this and finally decided to enlarge the original book so that it was now The History of Scepticism from Erasmus to Spinoza, which was published by the University of California Press in 1979.
In light of new material, new ideas, and the growing contributions of other scholars, I decided about five years ago to undertake what I suppose will be the final version of the story. By this time, I had been made aware that the initial impetus to studying the ancient sceptical texts developed in Florence at the end of the fifteenth century. The Dominican monk Savonarola, his associate Giovanni Pico della Mirandola, and his disciple Gianfrancesco Pico saw that the text of Sextus Empiricus, the major text we have of ancient Greek scepticism, was the source of the rejection of all forms of pagan philosophy. These three figures, I now knew, were responsible for making European thinkers aware of the power of sceptical arguments. So I wanted to start the final version of the book at this point in European history—when Greek thought was being transmitted into Europe and being translated into Latin and current European languages.
I also wanted to fill out much more of the background of the religious currents that became involved with the use of sceptical ideas. I wanted to show the influence of Spanish Jewish thinkers, renegade Catholics, and offbeat Protestants in using sceptical materials against their opponents. Besides enriching the background material, I also wanted to include various seventeenth-century philosophies as reactions to, or compromises with, the sceptical arguments. Therefore, chapters have been added on Thomas Hobbes, the Cambridge Platonists, the philosophers of the Royal Society of England, Nicolas Malebranche, and Gottfried Wilhelm von Leibniz. In addition I wanted to include the ongoing sceptical movement up to the end of the seventeenth century, including Pierre Gassendi, Simon Foucher, Bishop Daniel Huet, and the supersceptic Pierre Bayle. It is hoped that these enlargements will provide a better picture of how scepticism became so important in the beginning of modern philosophy and how it has been, to paraphrase Karl Marx, the specter haunting European thought. I have tried to take notice of recent scholarship by others and to at least mention any disagreements they may have with my picture of our intellectual history. The bibliography is not exhaustive but should provide a substantial basis for further research.