'The central thesis of the essays and lectures gathered together in this stimulating volume is that our knowledge, and especially our scientific knowledge, progresses by unjustified (and unjustifiable) anticipations, by guesses, by tentative solutions to our problems, in a word by conjectures. Professor Popper puts forward his views with a refreshing self-confidence.' - The Times Literary Supplement

'Professor Popper holds that truth is not manifest, but extremely elusive, he believes that men need above all things, open-mindedness, imagination, and a constant willingness to be corrected. In summarizing his views in this way, I have done scant justice to the subtlety and importance of his argument. His own presentation of his case is luminously clear.' - Maurice Cranston, Listener

'Popper holds that truth is not manifest, but extremely elusive, he believes that men need above all things, open-mindedness, imagination, and a constant willingness to be corrected.' - Maurice Cranston, Listener