Feyerabend wrote “Against Method” within a year and later remarked that, with it, he had said everything he ever wanted to say. However, the sharp criticisms that followed its publication took their toll on him. Perhaps he already suspected, while working on “Against Method,” what might be in store for him. And possibly, this is also a reason why, in parallel to this book, he worked on a manuscript with which he sought to correct the image of himself as a frivolous thinker. In 2004, Helmut Heit and Eric Oberheim discovered a book manuscript on natural philosophy in the Feyerabend estate in Konstanz. Feyerabend had begun working on this manuscript in the early 1970s and later apparently revised it with the intention of publishing it in 1976. The manuscript on natural philosophy was not published during his lifetime and was only made available in 2009, thanks to Heit and Oberheim. At its core, Feyerabend's aim in this book is to demonstrate how the rise of rationalism unfolded from early times through antiquity to the modern era. Scientific theories, as well as myths, are the results of human activities and can serve as guidelines for human actions. Their functionality or practicality is not shown in their truth value, but in whether and to what extent they can contribute to promoting social progress within a community.