Preface

• New: I have been engaging with the topic of rationality and critical thinking for many years, and I discover something new every day. This is an online book, and so I can always add new material and correct mistakes.
• Important: Since the Greeks, philosophers have stressed the importance of rational discourse. Where power is in play, interests are pushed through, and so the truth is readily sold as a mere "point of view": reality is then twisted, responsibility is relativised, and the obvious suddenly seems merely apparent. The Sophists already showed how, with rhetorical skill, one can even declare the guilty party — the proverbial bloody knife in hand — to be innocent.

Yet, ever since antiquity, one thing has become clear again and again: rationality is not arbitrary; it follows rules that can be learned, applied and checked.

A well-functioning political community thrives on healthy dialogue, and that requires citizens who think along critically, fairly and constructively.

• Personal: If you believe that politics is only for politicians, you will still get your money's worth here. Here you might just learn how, at the next family gathering, you can argue with your uncle in such a way that you both learn something without immediately going for each other's throats.

• Different approaches: different authors treat this topic very differently, depending on personal preferences and needs. Some show us first and foremost how important critical thinking is in everyday life. The psychologists show us the influence of cognitive errors and emotions on our thinking. Those with political interests concentrate on our so-called "post-factual" age, the influence of the media and the state of the sources. Those of a philosophical bent dive deep into the history of rationality and philosophy. The logicians shed light above all on the formal aspects and the logical errors of arguments, and the rhetoricians remind us that in the end we want to convince someone.

A Word on the Style and Scope of This Tutorial

• These pages aim to be both an introduction and a handbook or user's manual on the subject of critical thinking.
• Everything you find here has long been known, but is unfortunately not always easy to find, or is scattered across the web.
• Here you should find the things that matter, along with pointers to further reading (online where possible).
• This tutorial is very strongly structured. You have a menu for the whole book, and every article has its own menu. Everything is organised into points and sub-points. If you prefer philosophical outpourings, you had better read Sartre or Adorno, and if you would rather read prose, buy yourself a novel. Everything has its place — here we want to try to be clear and plain.
• The original text is in German. I delegated the English and French translation to artificial intelligence and corrected it in most cases, but not always. So if something strikes you as odd in the English or the French, just take a look at the German original.