In 2008 the Spinoza-Gesellschaft ran an international prize-essay competition entitled: How Much of Man is Natural? This book contains the winning essay which, in September 2008, was presented to the international conference of the Society in Marburg, Germany. In the preface and introduction the author reflects on the theme and the content of the winning essay. Three years after winning the competition the author decided to re-write the winning essay and this modified version of the winning essay is also included in the book.