We share the capacity for knowledge with animals, but it is the nature and the scope of what we may rationally believe that makes us human. Yet what kind of beliefs do qualify as 'rational'? This challenging and refreshingly innovative book addresses certain fundamental questions concerning rational legitimacy of some widely held beliefs and provides argument-based answers to such questions, while at the same time encouraging the reader to actively engage with the views put forward and form his/her own judgement. The book is typically discursive rather than simply informative, and introduces philosophy by doing it.