This book was conceived, written and published in Italian at a time
when Sir Karl Popper was still alive and active. It therefore seemed
fitting, for the English translation, to update the biographical
information as well as the bibliography. I did not think it necessary to
make any major changes, because the aim of this work is to draw out
the main lines of Popper’s thought and to show that they remained
constant through the evolution of his huge body of writings.
The Italian text was, however, intended for a public familiar with a
cultural context that is not exactly the same as that of the Englishspeaking
countries, and so the present edition differs at certain points
from the original. I have also adopted a number of suggestions made by
Professor Pieranna Garavaso of Minnesota University, who very kindly
read the text and commented on it in detail. I would like to thank her
most warmly for her invaluable remarks, which helped me in no small
measure to improve the book and to make it more suitable for Englishspeaking
readers. I am well aware that my survey of Popper’s thought is
not free from gaps, and probably also misunderstandings, but for these I
am, of course, alone responsible.