I’ll add something to Ratto’s and GE2’s comments. I tried to be brief! Sorry I was not. Some Marxists will disagree with the following summary. I am not suggesting that mine is the only or the best interpretation. I may even be wrong. Please feel free to ask more questions and I’ll help if I can.

Dialectical materialism, or materialist dialectics, is the theory of Marxism. Historical materialism is the application of dialectical materialism to human society.

Did Marx explain his method?

Marx did not explain what he meant in great depth. To figure out his method, we have to work, mainly, with the German Ideology and the Postface to the Second Edition of Capital, Vol I. There are lots of examples of Marx ‘doing dialectical materialism’. Those texts can be analysed to understand the method. These include the ‘Eighteenth Brumaire’, Capital, and, with Engels, the Communist Manifesto.

We can also read Hegel, as Marx was his student and learned dialectics from him. Marx turned Hegelian dialectics upside down. He borrowed the ‘rational kernel’ from Hegelian dialectics and dismissed the mystification. You can be forgiven for thinking that materialist dialectics are still mystical. It is a difficult method to understand.

Once you do understand dialectics and as you are beginning to understand them, you may experience a kind of double vision. It can make you feel disoriented at first because everything looks different through this lens. The method is what allows Marxists to reveal and explain processes that non-Marxists confuse, mistake, or are unable to explain.

Marx says the climb to scientific knowledge (i.e. a dialectical materialist world outlook) is steep and treacherous but climbing up to the summit is worth it. This emphasis on science is why Marxists call themselves ‘scientific socialists’. Marxists today apply dialectical materialism even to the works of Marx, Engels, Lenin, etc.

In this sense, a Marxist could and should disagree with arguments made in the orthodox texts, even major arguments, and still call themselves Marxists. Lenin (IIRC) described the method as ‘the concrete analysis of concrete conditions’. Marx: the ‘ruthless criticism of all that exists’.

There is an anecdote that Bertell Ollman got into trouble for teaching his students dialectics. He replied that it would be a disservice not to teach them, because once someone learns dialectics they very quickly see that all other methods are incorrect. Maurice Cornforth makes a similar argument in The Open Philosophy and the Open Society (this is a critique of Karl Popper’s, The Open Society and it’s Enemies, an influential anti-Communist text). This idea may be the root of the meme, ‘the immortal science of Marxism-Leninism’.

Dialectics can be traced back, as already stated in this thread, to ancient Greek thinkers. That’s where we hear the idea that one cannot step in the same river twice. That’s a good image for realising that the only constant is change. Hegel gave this idea a systematic framework. Marx accepted (or seems to have accepted) that framework but he begins by examining the river, rather than thinking about the river.

Others have been helpful, too. Engels clarified some parts of the method in Anti-Duhring, in Dialectics of Nature, and Socialism: Utopian and Scientific. Lenin wrote ‘Three Sources and Three Component Parts of Marxism’ on this topic. Stalin wrote ‘Dialectical and Historical Materialism’. Mao wrote ‘On Contradiction’. There are many other sources focusing on this method and some that just ‘do’ historical materialism while making only a few side-comments about the method.

So what is dialectics?

Dialectics is the study of change. It offers a way of looking at the world and everything in it as connected, in a ‘totality’. Dialectics does not see ‘things’. Instead, it sees ‘internal relations’ and ‘processes’.

There are four key, interconnected parts to the method. In a way, these are just different ways of explaining the same concept.

1. Contradiction. E.g. capitalist society comprises two main classes, constantly struggling against each other. Without one of these classes, there can be no capitalism.

2. The unity and interpenetration of opposites. The bourgeoisie and the proletariat are unified in a single system and one cannot exist or be defined or understood without the other. I.e. there can be no employee without an employer, no parenthood without childhood, no magnet without a North and South pole.

3. Identity and difference. As opposites are internally related, these opposites are at the same time identical and different.

4. The transformation of quantity into quality. This means progress is not a straight line. Instead, progress happens little by little, then leaps. Heating water by one degree at a time just results in warmer and warmer liquid. Until it boils and turns into a gas, steam. The other way round the water gets colder degree by degree until we can no longer call it water because it has transformed in quality and become ice.

If all is contradiction, can Marxists ever be wrong?

Some people criticise dialectical materialism and the notion of contradiction because it seems to provide a way out of being wrong. If someone points out an error, says the critic, the Marxist can reply, ‘Ah but I’m still right because two contradictory answers can coexist’.

Maurice Cornforth explains the problem. The critic has misunderstood the place of contradiction. The Law of Contradiction still rests on logic. Imagine an issue that has two sides, A and B, which are contradictory. One person could examine only B (in capitalism the bourgeoisie) and another could examine only A (in capitalism the proletariat). Their answers will be contradictory, neither will be right, and both thinkers will criticise the other for a one-sided analysis.The Marxist explanation will combine A and B, so that the answer accounts for the contradiction (in capitalism there is a bourgeoisie and a proletariat).

There are idealist dialectics and materialist dialectics. Hegelian dialectics are idealist.

And what is materialism?

Imagine a chair and a table in your home. Does the furniture exist because you have imagined it? Or can you imagine the furniture because it exists in the real world? For the idealist, the idea comes first. For the materialist, the physical furniture in the real world comes first.

The dialectical materialist can accept that if a carpenter imagines a chair, she can build one out of wood, screws, and fabric. So there is a place for the idea in the materialist worldview, but the real world comes first.

Not all materialists are dialectical. Some are mechanical, for example. Sometimes anti-communists say, ‘But why do we need Marx: he wasn’t that revolutionary; others were doing materialism long before him.’ Others were doing materialism before Marx (e.g. Feurbach), who acknowledges this. The problem is that materialism without dialectics lacks explanatory power.

So what is dialectical and historical materialism?

Marxists look for contradictions within material social relations. Then it is possible to identify the unified opposites that will struggle. This is useful because this struggle drives change. In physical sciences: an atom is the struggle between protons and electrons. Figure out that puzzle and you can have nuclear power stations. In social sciences: the struggle between the monarchs and feudal lords against a growing class of merchants transforms society from feudalism to capitalism. Figure out that puzzle and you can have revolution.

This method is what leaves Marxists looking for the class content, or class character, of relations. That class content is always present within relations in class-based society, such as capitalism. This allows Marx and Engels, e.g. to understand that there can be bourgeois or conservative socialism as well as proletarian socialism in the Communist Manifesto (chapter 3, section 2).

Without dialectics, the non-Marxist can get into endless debates about socialism and fail to understand how (working class) socialism gets derailed by the ruling class and distorted by the kind of politics that focuses on and ends with elections at the ballot box. Seeking to understand the class character of socialism makes it is easy to see that there are conservative socialists and that they imagine a world with all the benefits of capitalism without the oppression: a bourgeois world without a proletariat. Dialectics shows this is nonsense and leads to slogans (e.g. about human rights) or, at best, reformism. Never revolution. Even the conservative socialist may acknowledge some contradictions of capitalism, but without dialectics they misdiagnose the cause and so cannot provide a workable solution. That solution is moving past capitalism and its contradictions.

Historical materialists argue that history is made by class struggle and that political economics is ‘historically contingent’. This is a complex label for a quite straightforward idea. It means that capitalism came into existence at a certain time, under certain material conditions, and that it will disappear at a later time under new conditions.

Without class analysis, it looks like there has always been capitalism because there has always been trade. It may be that ‘society’ comes into existence when humans start to create their own means of subsistence and begin to exchange. The capitalist, though, assumes that this means all society has been capitalist. If that’s true, then all future society will be capitalist. A depressing thought.

Dialectics shows this claim is false. There may have been markets and trade for all or most of human society, but capitalism arises when people need to use markets to survive. While the majority of European peasants can survive by working two days a week on their own farm and three on the lord’s farm, they can generally survive without the market, and there is no capitalism. Today, if you want to eat, wear clothes, live under a roof, you need to engage with markets and buy those things. All the means of subsistence have been ‘commodified’.

Commodities are a core part of historical materialist analysis, explained the the first few chapters of Capital. A commodity is, dialectically, a unity of use value and exchange value. The mode of production in capitalism is commodity production.

The means of subsistence (and non-essential goods and services) are produced to sell, for their exchange value. This is only possible because commodities have a use value, which is what consumers want. The contradiction is that commodities represent both use value and exchange value, but they cannot be realised at the same time. You cannot eat a cake and sell it (unless you’re a successful fraudster, but even the fraudster hasn’t really sold the cake, but the merely promise of a cake). To the historical materialist, the contradictions of capitalism flow from this contradiction within the commodity.

It is important to note that historical materialist analysis begins with concrete conditions, but the explanation may start with abstract ideas. Marx says the method of presentation is different to the method of analysis. He was talking about Capital, which begins with the abstract commodity before considering e.g. the working day, technology and machines, and ‘bloody legislation’ that punished rural peasants who did not go to work in a factory after the commons were enclosed.

This explanation probably raises more questions than answers, but I hope it helps.

Again, people may disagree with this explanation and that challenge is welcome.