Bertrand Russell described this study, with its companion volume on Hegel and Marx, as 'a work of first-class importance which ought to be widely read for its masterly criticism of the enemies of democracy, ancient and modern. His (Popper's) attack on Plato, while unorthodox, is in my opinion thoroughly justified. His analysis of Hegel is deadly. Marx is dissected with equal acumen, and given his due share of responsibility for modern misfortunes. The book is a vigorous and profound defence of democracy, timely, very interesting, and very well written'.
'A powerful and important book. It is a criticism of a set of dogmas which underlie the most influential political theories, and in consequence powerfully affect the actual conduct of human affairs. Dr Popper writes with extreme clarity and vigour. His studies in Greek history and Greek thought have obviously been profound and original. Platonic exegesis will never be the same again. Nor, I think, will Marxist exegesis. Readers should not miss studying the notes collected at the end of the two volumes.' - Gilbert Ryle, Mind