Second, it ignores the actual, real distinction between Marxists and anarchists, which is centralization and decentralization, originating from differing views on historical materialism and idealism.

Anarchists want to break up society into decentralized units, they see the centralization tendency of capitalist society as a bad thing and want to smash it and build an entirely new and different society out of a void, while Marxists see the development of capitalist society as in fact laying the foundations for socialism which it will be built on top of, i.e. it will be centralized.

Bukharin explained this brilliantly a century ago.

Communist society is, as such, a STATELESS society. If this is the case - and there is no doubt that it is - then what, in reality, does the distinction between anarchists and marxist communists consist of? Does the distinction, as such, vanish at least when it comes to examining the problem of the society to come and the "ultimate goal"? No, the distinction does exist; but it is to be found elsewhere; and can be defined as a distinction between production centralised under large trusts and small, decentralised production.

...Our ideal solution to this is centralised production, methodically organised in large units and, in the final analysis, the organisation of the world economy as a whole. Anarchists, on the other hand, prefer a completely different type of relations of production; their ideal consists of tiny communes which by their very structure are disqualified from managing any large enterprises, but reach "agreements" with one another and link up through a network of free contracts. From an economic point of view, that sort of system of production is clearly closer to the medieval communes, rather than the mode of production destined to supplant the capitalist system. But this system is not merely a retrograde step: it is also utterly utopian. The society of the future will not be conjured out of a void, nor will it be brought by a heavenly angel. It will arise out of the old society, out of the relations created by the gigantic apparatus of finance capital.

—Bukharin, Anarchy and Scientific Communism

It is very important to understand that anarchists aren't simply Marxists who want to get to statelessness faster. They are in many ways the polar opposite of Marxists, the gulf that separates Marxists from anarchists is just as large as pretty much any other ideology.

Anarchists reject historical materialism and view history through an idealist lens, believing that all new societies are "conjured out of a void" as Bukharin put it, and thus they believe this new society can be anything they want it to be, if they can imagine it then it can be implemented.

Marxists on the other hand, with a historical materialist analysis, see new systems as inherently being built upon new conditions brought into existence by the old system, i.e. socialism cannot be anything we want it to be but must be built upon foundations created by capitalism itself.

Hence, Marxists see the centralization tendency of capitalism as the basis for what socialism will be built upon, while anarchists not only do not hold this view, but they view the conditions capitalism is bringing forth as a bad thing that must be entirely destroyed.

A wide gulf separates socialism from anarchism, and it is in vain that the agents-provocateurs of the secret police and the news paper lackeys of reactionary governments pretend that this gulf does not exist. The philosophy of the anarchists is bourgeois philosophy turned inside out. Their individualistic theories and their individualistic ideal are the very opposite of socialism. Their views express, not the future of bourgeois society, which is striding with irresistible force towards the socialisation of labour, but the present and even the past of that society, the domination of blind chance over the scattered and isolated small, producer.

—Lenin, Socialism and Anarchism

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