Thoughts are free - but they are no longer secret. Today, our data is automatically stored and analyzed by algorithms ”behind the cloud” - where we no longer have control over our data. Our most private and secret information is entrusted to the internet and permanently collected, stacked and linked to our digital twins. With and without our consent. "Privacy is dead", as Mark Zuckerberg put it.  The question is: How did we get there? And, if the actors behind the cloud know everything: what is still private today, and are there any personal secrets at all when the "gods" behind the cloud possibly know us better than our friends and family? The book uses a wealth of case studies (e.g. cryptocurrencies, journalism, digital traces of sexual preferences) to develop a typology of privacy in the history of ideas. Furthermore, it shows the areas of life in which big data and artificial intelligence have already made inroads. This book is a translation of the original German 2nd edition Die Rückseite der Cloud by Peter Seele and Lucas Zapf, published by Springer-Verlag GmbH Germany, part of Springer Nature in 2020. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation.