The first point relates to our understanding of the last century, a very crowded and eventful one in world history. The progress of Marxism is itself subject to dialectical laws and inner contradictions, which reveal themselves most clearly in crisis situations. Most Marxists would accept that the parties of the Second International, although subjected to a sharp critique at the time by such thinkers as Rosa Luxemburg, showed their bankruptcy during the First World War. The future of the international labour movement then lay in the hands of those who had opposed it, the Zimmerwaldians, Lenin, Trotsky and the founders of the Third International.

This also proved to be the case with the parties founded by the Third International. Stalinism revealed itself to be a new, different process of degeneration and corruption. After leading the working class to repeated betrayal and defeat, the USSR has finally collapsed into a species of undeveloped mafia-capitalism, a pattern that is clearly now being followed by such countries as China and Vietnam, for those with eyes to see. Now the critique of Stalinism – the degeneration of a revolution afterwards, as opposed to accommodation to bourgeois society in the first place – is Trotskyism, and those who have failed to go through this school are just as incapable of taking Marxism any further as those who failed to learn from the collapse of Social Democracy in 1914. And because Trotskyism was a critique of Stalinism, it was quite adequate for as long as this phenomenon existed in the USSR. Only its failure to mark out a new path since then has led to its growing incoherence and irrelevance during the past decade.

Moreover, only those who proved their hostility to Stalinism – and the Trotskyists proved it often enough at the cost of their lives – can appear before the class with a claim to represent a higher civilisation. The mass murder, grinding tyranny, megalomaniac ruler worship, palpable lying, crushing of the human spirit, waste of human life and natural resources – and the list could go on for several pages – of official "Communism" have made the word stink in the nostrils of the working class, and it will be some time before we are able to convince it again that communism means more freedom than bourgeois society, and not less. The future of socialism, communism and Marxism can only belong to those who can show that they were not party to this traumatic and deeply demoralising experience.

The terms used by Trotskyists to grapple with this unforeseen degeneration, and the controversies involved in them, have evoked much mockery among those who write them off as sectarian religious squabbles. But unless there is clarity about such terms as state, class, mode of production, caste, substitutionism, Thermidor, Bonapartism, etc, an entire epoch in human development cannot be accounted for. And such clarity can only emerge from a clash of ideas, as it always did. No other current at the time was conscious of the importance of these terms, let alone able to apply them.

Moreover, in undertaking this analysis, Trotskyism restored to Marxism its sense of movement. In arriving at the concept of the "degenerated workers’ state" in The Revolution Betrayed, Trotsky placed his emphasis upon the development of the Soviet Union up to 1936, as opposed to remaining at the stage of fixed definitions. In In Defence of Marxism he went further, pointing out that if the end of the Second World War did not turn out as expected, this view of the Soviet Union, as well as our concept of the epoch, would require further definition and elaboration. As the last decade of the last century proved, the process he outlined ended in the utter collapse of the structure. This alone should serve to remind us that a "Marxism" that takes no account of the movement of phenomena is not only arid, but useless.

Another of Trotskyism’s undoubted legacies lies in restoring to Marxism its transitional character. In separating immediate aims from the ultimate goal, both Social Democracy and Stalinism marked a step backwards from the Marxism of Marx. Marx’s method for the twentieth century is encapsulated in the Transitional Programme. In saying this, I do not intend to claim that we should follow this programme to the letter – every programme put forward by the movement at any time has to answer to current events and needs – but the stages theory of creating revolutionary organisations simply does not meet the urgent demands of our time. Never has the gap been so alarmingly wide between the urgent tasks of the day and the present small size and political impotence of the revolutionary organisations.

The method recommended by Trotsky is to speak in terms of already existing working class organisations that have the material power to alter the direction of politics. (Nothing is more alien to transitional politics than to demand that the class should have to wait until a revolutionary organisation has recruited enough people to affect the issue – a sort of "come and join us, and nothing can really be done until we are large enough".) Trotsky proposed that this should be done by placing demands upon the leaderships of those institutions that enjoy the support of the majority of the class – in our case, the trade union and Labour Party leaders. Only in this way can Marxism fulfil the function for which it was designed – providing the institutions of the working class with a viable programme for our time.

One of Trotsky’s earliest insights was into substitutionism, the risk that those who speak in the name of the working class will politically disenfranchise the class itself. Rosa Luxemburg was also aware of this, but Trotsky’s early statement of the problem was proved almost to the letter by the experience of the first decade of the October Revolution, not least by his own actions at the end of the Civil War and the arguments he developed in Terrorism and Communism. The CPSU represented the working class probably for less than two years, but spoke falsely in its name for another seventy. Now for anything to exist, as Hegel pointed out, it is necessary that it should exist. And the Soviet state did correspond to the logic of necessity for a time, but only within well defined limits – when the state was substituting for a non-existent bourgeois class in the process of primary accumulation. That limited role was already played out by the 1980s. History has now demonstrated that, however long such artificial structures last, they are still crisis phenomena, bound to topple over into something else in the end.

The task of the emancipation of the working class remains that of the workers themselves, and here again Trotsky’s analysis of what Khrushchev called "the personality cult" is the classic statement of the question. We may well argue that Trotsky did not go far enough, and that he should have taken a sledgehammer to the Lenin cult as well, which after all was first put together as a weapon against him. And it is doubly ironic that there should now be a cult of Trotsky among the Trotskyists, not to mention even more degenerate cults, such as those of Castro or Mao Zedong. Yet it is still true that Trotskyists share with the Anarchists the honour of promoting the self-activity of the working class, and of defending, however lamely, the idea that it is a deception to talk about socialism unless this class, conscious of its historic tasks, takes and wields power through its democratic institutions.

Only a couple of years after his remarks on substitutionism came another seminal contribution by Trotsky, to what is often called the Law of Uneven and Combined Development. It is doubtful whether this should, in fact, be accorded the status of a law, but in any case Trotsky’s Theory of Permanent Revolution is an indispensable elaboration of it. Here again, it is, of course, already present in Marx’s Address to the Communist League, as well as in the thought of Rosa Luxemburg, but they were never to witness the almost mathematically exact demonstration history afforded Trotsky in 1917. And as the phenomena discussed these days under the heading of "globalisation" make us all aware, the penetration of the market into social relations all over our planet makes it impossible to believe that all societies will follow the pattern of human progress upheld by those who still cling to stages theories of the Stalinist type.

But since it appears that Trotskyism itself has degenerated, some sort of training in an older school is an invaluable asset. As John Sullivan once remarked: we know what stopped the functioning of Trotsky’s brain – it was an ice pick – but opinion is divided on what has produced the same result among his followers.

As opposed to those who worship the Zapatistas, the Latin American guerilla, etc, the older Trotskyism taught us that there is no such thing as a peasant state, or peasant socialism. In building upon the insights of Marx (who called the peasant mentality "a sack of potatoes"), of Plekhanov and of Lenin’s Development of Capitalism in Russia, Trotsky showed that the peasantry, not being a primary class, cannot wield state power, and must either ally with the working class or be subject to a state erected by others. Nothing in the history of Yugoslavia, China, Vietnam, Cambodia or anywhere else since 1940 has provided anything but negative confirmation of Trotsky’s view of this question. Moreover, however much it may distress romantics, the rapid industrialisation of the Third World confirms history’s verdict that the peasantry is an obsolete, dying class.

For those who feel that revolutionaries can fall in amicably with bourgeois parties, whether it be the Greens or any other, a further great achievement of the older Trotskyism was its critique of class collaboration via the Popular Front. Here again, the essence of this critique can be found in the Second International, in the debate over Millerandism at the beginning of last century, but its classic expression is surely Trotsky’s analysis of the disasters of 1936 in France and Spain.

The front in which revolutionaries should involve themselves is, of course, the workers’ United Front. Again, those who gave the bourgeois state thousands of pounds in the electoral adventure of the Socialist Alliance, fondly believing that they were taking part in a United Front, might explore again Trotsky’s writings on what a United Front actually is, The First Five Years of the Communist International in particular. There they will find that the United Front is not a temporary non-aggression pact between sectarians, but an attitude to be adopted by revolutionaries towards the mass movement, and the policies that flow from this.

And the over-debated question of entrism, as Trotsky defined it in his writings on France, is simply where revolutionaries take their place on the inside of the United Front they want to see formed, a tactic which is forced on them when they have no mass base of their own to bring to the alliance. Class conflict is bound to express itself sooner or later inside class institutions. The votes had hardly been counted – and it did not take very long to count the Socialist Alliance’s votes – when the real class conflict with Blair’s government reflected itself in the trade unions and the Labour Party, but our revolutionaries were in no position to take advantage of it.

Another area where the sternest critic of Trotskyism is Trotsky himself is internationalism. However false the existing "Fourth Internationals" – and I, for one, have lost count of how many there are of them – there is still a crying need for a World Party of Socialist Revolution, such as he attempted to found in 1938. For want of an International, Trotsky’s followers subordinate themselves to bourgeois nationalism from Ireland to Israel, and particularly in the Balkans, where he refused to take sides, as he makes clear in The Balkan Wars. They also seem unaware that the early Comintern made it clear that support for the national claims of oppressed peoples is not to enable bourgeois nationalists to emancipate them, but is meant to expose their impotence to do so – an exact parallel with the Comintern’s policy towards Social Democracy in western Europe.

But here we touch upon the broader and more embarrassing question of where the present policies of the Trotskyists come from, if it is not from Leon Trotsky. Since class questions are placed well in the background, at least among Trotskyists in Britain, and issues such as sex, race, ethnicity, nation, religion, ecology, etc, are more generally debated, the conclusion is inescapable that they get their agenda from such papers as the Guardian, and their Marxism really functions as the left wing of liberalism.

Well might Trotsky echo the words of Wellington reviewing his troops before the Battle of Waterloo: "I don’t know what they do to the enemy, but by God they frighten me"!