This biography of the founder of critical rationalism gives an insight into a complex and fascinating personality and into the making of one of the 20th century's most influential philosophical theories. As a modern representative of Enlightenment, Popper emphasized the role of criticism both in the fields of science and social reforms. As "learning by mistakes" became the only way of social and scientific progress, Popper changed our perception of scientific knowledge and redefined our concept of democracy as an "open society." A new chapter on "Popper's Traces in the Present" is included in this book.