As the essays in this book point out, there is no one answer to that question. There are, instead, many answers, and additional questions.
In history, it's not so much a case of arriving at the "truth." Rather, it's the journey of discovery that really counts. The essays Weber has collected run the gamut, from turgid academic writing and sniping to refreshingly clearly-stated prose. His introduction is masterly, the bibliographic references invaluable, and the overall effect one of having learned just how complex and diverse the causes of an effect can be.
Highly recommended for readers interested in this area, especially for classroom use at the college and university level.