Leszek Kolakowski is one of the great thinkers of our time, author of numerous books on philosophy and religion, recipient of many honors and awards. He left his native Poland in 1968, after being dismissed from his teaching position at Warsaw University and expelled from the communist party for unorthodox views. He went on to a distinguished academic career in the West – teaching at McGill University in Montreal, the University of California, Berkeley, and Yale – and today divides his time between All Souls College, Oxford, and the University of Chicago.

The publication of the new, one-volume edition of his monumental study, “Main Currents of Marxism” (W.W. Norton, 1,283 pages, $50) is a welcome occasion for some reflections on his achievement, as well as the part played by Marxism in 20th-century intellectual history. Not only is “Main Currents” the definitive history of Marxism; it is its definitive critique and demystification. This huge study examines every aspect of this revolutionary political philosophy: its origins, interpreters, the schools of Marxism in both the 19th and 20th century, and the disputes among them. Mr. Kolakowski conceived of the study as “an attempt to analyze the strange fate of an idea which began in Promethean humanism and culminated in the monstrous tyranny of Stalin.”

It is impossible to summarize a huge work such as “Main Currents” in a brief review but some of its major propositions can be noted. The most important and instructive is that Marxism is essentially a secular religion, a product of utopian impulses influenced by 19th-century romantic longings and faith in the limitless perfectibility of human nature and social institutions. Living in communist Poland doubtless helped Mr. Kolakowski to understand the unwelcome results of the attempted realization of these theories. He wrote:

The influence Marxism has achieved, far from being the result or proof of its scientific character, is almost entirely due to its prophetic, fantastic and irrational elements. Marxism is a doctrine of blind confidence that a paradise of universal satisfaction is awaiting us … it is a certainty not based on any empirical premises … but simply on the psychological need for certainty … Marxism performs the function of a religion and its efficacy is of a religious character.

At the present time, few political systems continue to claim that they are faithfully applying Marxist theory to their political and economic practice or are even inspired by its ideas. The only exceptions are North Korea and Cuba. (China and Vietnam pay some lip service to the Marxist heritage while rapidly privatizing their economies.) In Western capitalist countries Marxism mostly survives as an academic pursuit of intellectuals estranged from their societies. The moralistic rejection of capitalism remains the major strength and appeal of Marxism – something being revitalized by the hostility to globalization.

“Main Currents” was written between 1968 and 1976, well before the collapse of Soviet communism, a political system that justified itself by Marxism and claimed to be splendidly guided by it. Mr. Kolakowski had experienced in Poland how little help Marxism offered in the creation of a more humane, rational, and just society, let alone a freer one.

Western Marxists vehemently argue that the disaster of Soviet communism has no relevance whatsoever to the great truths and insights Marx and his followers dispensed. They dispute just what kind of a contribution Marxist ideas made to the socialist states that arose and expired in Eastern Europe – what was the true relationship between theory and practice? They argue that the Eastern European communist states collapsed because of the discrepancy between Marxist theory and Soviet practice. To the contrary, these states failed because they did rely on Marxist ideas in the building of a new social system.

It is possible to resolve the dispute about the effect or influence of Marxism on the policies and institutions of the various communist states by separating policies and the practices that diverged from the theory from those that were congruent with it. The most glaring discrepancy between theory and practice (or the theory and the anticipated results of its implementation) emerged in the economy: The nationalization of the means of production created neither a more egalitarian nor a more productive and efficient society. As Mr. Kolakowski wrote:

Marx seems to have imagined that once capitalists were done away with the whole world would become a kind of Athenian agora: one had only to forbid private ownership of machines or land and, as if by magic, human beings would cease to be selfish and their interests would coincide in perfect harmony.

It did not happen; instead these systems developed chronic shortages, diminished work ethic, and a deeply alienated work force. The one-party dictatorship provided fewer avenues for political participation than the parliamentary system in pluralistic societies. The rise of supremely powerful dictators surrounded by compulsory cults flew in the face of the Marxist belief in the unimportance of the individual in the historical process. The proletariat did not become the ruling class, and the workers were not persuaded that they were the masters of their own fate or owners of state property. Neither religion nor crime withered away, notwithstanding the Marxist belief that the first was an opiate of the masses (produced by the hopelessness of life in a capitalist class society) and the second a direct response to the poverty, exploitation, and inequality such societies perpetuated.

Nonetheless there was no divergence between theory and practice as far as the intention and policy of abolishing the private ownership of the means of production was concerned. It was embraced and zealously implemented in all communist states from Albania to Vietnam – despite the obvious economic price it exacted – especially in agriculture and the production of consumer goods. These may have been unintended consequences, but they originated in Marxist beliefs and presuppositions.

There was further congruence between theory and practice as regards the doctrine of class struggle. It was eagerly embraced in all communist systems and provided historical and theoretical legitimacy for great surges of political violence and coercion. It directly led to punishing people not for what they did but for what they were – their opinions and beliefs inferred from these affiliations alone.

The belief in the omnipresence and inexorability of class struggle desensitized its practitioners to the results of their policies; it also succeeded in persuading them (relying on Marx’s fantasies about the ultimate withering away of the state) that the generous use of repression would pave the way toward a social system where none would be needed. Theory also became institutionalized in the attempted coercive elimination of religious beliefs and practices – a policy adopted thanks to Marx’s great contempt for organized religion.

The discrepancy between theory and practice did not mean that no effort was made to implement Marxist ideas, but that the attempted implementation failed to yield the anticipated results; there was a yawning gulf between the promises, ideals, and expectations the theory fostered and the results of their attempted realization – but not between the theory and the policies and institutions which were devised to implement them.

Mr. Kolakowski rightly emphasized that “no political or religious movement is a perfect expression of that movement’s ‘essence’ as laid down in its sacred writings; on the other hand these writings are not merely passive but exercise an influence of their own on the course of the movement.” He has given us invaluable help in understanding what it was in these ideas that lent itself to misuse or distortion, to the institutionalization of inhuman ruthlessness dedicated to receding ends.

It is safe to say that Leszek Kolakowski’s work will remain important and appreciated as long as ideas have an impact on history and human behavior.

Mr. Hollander, a professor emeritus at the University of Massachusetts at Amherst, is the author of numerous books on communist systems and their Western perceptions. His anthology “From the Gulag to the Killing Fields: Personal Accounts of Political Violence and Repression in Communist States” will be published by ISI at the end of the year.