I feel like I understand communist theory pretty well at a basic level, and I believe in it, but I just don't see what part of it requires belief in an objective world of matter. I don't believe in matter and I'm still a communist. And it seems that in the 21st century most people believe in materialism but not communism. What part of "people should have access to the stuff they need to live" requires believing that such stuff is real? After all, there are nonmaterial industries and they still need communism. Workers in the music industry are producing something that nearly everyone can agree only exists in our heads. And they're still exploited by capital, despite musical instruments being relatively cheap these days, because capital owns the system of distribution networks and access to consumers that is the means of profitability for music. Spotify isn't material, it's a computer program. It's information. It's a thoughtform. Yet it's still a means of production that ought to be seized for the liberation of the musician worker. What does materialism have to do with any of this?
Sorry you're getting bad answers. There is actually a real answer to this.
The first part I think most people got right: you are using a different definition of materialism than Marx did.
What Marx means when he says materialism is where everyone is failing you. For example, Marx and Engels disagreed on Engels project to demonstrate that the physical world operates dialectically. Marx was very clear on his position: the metaphysical expression of that which is material is immaterial.
And here we have a glimpse of the meaning of materialism.
Material here is not a noun. It's an adjective. That which is material TO SOCIETY stands in opposition to that which is immaterial (not material) TO SOCIETY. Not "is it matter?" but "does it matter?"
Society exists in the real world. Human society is also socially constructed in the minds of persons. What is in the minds of persons is material to society, even if that which is in the minds of people refers to things that are immaterial.
How is this possible? It is possible when we use this definition of materiality:
That which is material is that which is causally linked.
That's it. Cause and effect are the easiest way to understand materiality. What is immaterial? Objective morality is immaterial. Whether something is objectively good or objectively evil has zero causal impact on the world (except mentally, but I will get to that). Whether morality is objectively real or not is also immaterial, again because of a lack of casual connection to anything. Platonic forms, also completely acausal.
So whether the expression of that causality is through substance or not is immaterial, in so far as the metaphysics has no bearing on causal relationships. If it turns out that matter is not real, as you say, we must still contend with cause-effect relationships. If your chosen metaphysics is closer to real reality than contemporary mainstream understandings, it will be judged so because it offers better explanatory power for society to bring about changes to conditions. The correct answer to what is reality is always material to society if it offers society causal mechanisms for effective change.
So what about beliefs? Persons act. That much is true. Those acts we call behaviors. Those behaviors are causally linked. They cause things to change. But what are behaviors caused by? Beliefs. Your behaviors are caused by your beliefs. And what causes your beliefs? Your experiences. Experiences cause beliefs, beliefs cause behaviors, behaviors cause changes in the world. That causes experiences? Changes in the world. So when someone behaves near you, you sense those behaviors and the changes those behaviors cause and you experience something and it causes changes to your beliefs.
Why does this matter? Well, if you believe in objective morality, your behavior will be different than if you did not. If you believe one thing to be good and another to be evil, those beliefs will impact your behavior. If those beliefs change, your behaviors will change. Therefore, what you believe is material to your behaviors, and your behaviors are material to society. Therefore, if we want to change society, we have to change it via behaviors and if the behaviors we observe are not the behaviors that will lead to the desired change then it becomes imperative to change beliefs. Knowing that beliefs change by experiences and that experiences are responses to change and change occurs through behaviors we can alter our behaviors to generate new experiences that will alter people's beliefs that will alter their behaviors that will alter society. In this way morality qua beliefs people have about morality is material but metaphysically objective morality is immaterial.
That's not what materialism means in the context of communist theory.
When communists talk about materialism, we generally refer to historical materialism, the theory that a society's culture and politics (its superstructure) are shaped by its material forces (its base). This isn't strictly a one-way street, mind - it's cyclical, with each exerting some influence on the other, though the base dominates. See this diagram. This view is generally contrasted with liberal idealism, which assumes that ideas and culture are the dominant drivers of society.
To give an example in the most straightforward terms possible, let's take the question: "What is the connection between the 19th century US southern aristocrats' Christianity and their support for slavery?"
Idealism says that these aristocrats were pro-slavery because they interpreted the Bible to be pro-slavery.
Materialism says that these aristocrats interpreted the Bible to be pro-slavery because they were pro-slavery.
Ultimately, they were following their economic and material interests in a society in which Christianity was the dominant religion. Anything they may have believed or professed to believe about Christianity emerged from that.
Idk if you're doing a bit, but assuming that you're serious and having read through some of your comments below, I think the problem that you're having is largely based in a misunderstanding of what people tend to mean when they argue that something is socially constructed. And, relatedly, that you're working from an opposition between the real and the imaginary that can't account for the complexity of their actual relation. Correct me if I'm wrong, but your basic assumption seems to be that if something is socially constructed then it is imaginary/'ideal' and, therefore, that isn't real/material. And, further, that if something is socially constructed then it emerges as a creation of the individual human mind.
The problem with the first assumption is that socially constructed forms are still real and material forms. Even what at first glance might appear as immaterial forms (such as the dominant ideas of a society or music) emerge from within a historical and material context that works to structure them and provide the conditions of possibility for certain ideas and forms to emerge, and these likewise operate back upon that context in real ways. To use your example of the commodities produced by the music industry, the apparent 'immateriality' of a song still depends upon a wide range of material forms. Among these are the material forms of the instruments used in its creation, the historical traditions of music and the material forms necessary for archiving and preserving them into the present of the song's production, the material networks that facilitate and determine the song's distribution (which include everything from the record companies that sign and promote artists, to the mines in which the raw materials that are used in the production of both the instruments being played and the computers and speakers upon which the song eventually comes to be heard are excavated). You can see here already that the relationship between the apparently 'ideal' and the 'material' is far more complex than a simple binary opposition.
This leads to the problem with the second assumption that you seem to be making, which is that you seem to be positing a genuinely idealist understanding of ideas and the human subject in which ideas emerge in the manner of a virgin birth from the individual human subject (this being the only form that would preserve their genuinely 'ideal' being from being muddied by a dirty materialism). The problem with this belief is that it fails to account for the historical production of that subject - a historical production which is, ironically, a key idea within social constructivist theories. Ideas are necessarily social forms, their existence implies intersubjectivity through the existence of language. In this sense, ideas necessarily have a material dimension that fatally undermines the kind of idealist conception that you seem to be expressing. This is because our individual subjectivity and thus our ability to have ideas emerges within a substrate that is outside and beyond us. We are already structured in certain ways as a condition of being able to think and this is the basis of a materialist understanding
I missed out on a lot of discussion, but if it hasn't been linked, I am once again asking every Hexbear to read Socialism: Utopian and Scientific.
The gist of what Marxists believe is that all things come from a material reality, even intangible things like music, religion, and ideas. They come from the human brain, which is itself influenced by the material world it observes and interacts with. So I would say that even though Spotify and the songs on there aren't "materials" in a certain sense, they are still things that require a material reality to produce them. You cant have music or spotify without musicians and programmers.
Because scientific socialism derives itself from a materialist analysis of human history. Scientific socialists realize you cannot understand history and society without analyzing the mode of production, which in turn depends on the relations of production and the productive forces. Let me give a brief example. Capitalism could not exist without certain technologies and certain classes. Advances in textile manufacturing that used hydropower (productive forces) allowed for the private ownership of factories owned by capitalists that employ an industrial proletariat (relations of production). The competing interests of these classes results in class struggle. Certain economic laws - namely the tendency for the rate of profit to fall due to the rising organic composition of capital (in other words, firms increasingly automate to gain a relative profit but once the entire industry automates, they lose profitability) - make this economic arrangement more untenable. Over time, capitalism makes it harder and harder for itself to continue, and the class struggle inherent in the system will overthrow it. That is roughly the materialist/scientific socialist conception of capitalism/communism.
As a worker, you're likely to have an impulse towards communistic ideals like "people should have access to the stuff they need to live" because it is in your class interest. But the bourgeoisie genuinely don't believe in this. Sadly, these ideals are not universal. A historical example would be the European enslavement of Africans. There were many liberals who despised it on principle, but it was an integral part of the economic system as well as being in the direct class interest of the ruling class for a very long time.
There were non-materialist communists. They were the utopian socialists of the 19th century.
What does materialism have to do with any of this?
material reality, in this case, is the concept of what does not go away once you stop believing in it. if it helps to view it like that, even if you don't believe in physicality, then there you go
Matter in the context of of philosophical materialism just refers to the external world that humans find themselves within. I suppose you don't have to believe in the explanations given by the field of physics to recognize this world as something that exists, if that's what you mean. Philosophical materialism is just the position that this external world and it's relationships (including to humans) have the primary role in determining human ideas, and that ideas have no other basis than the material structure and internal relationships of the human brain (no Ideals floating around in the ether that humans have discovered).
Materialism became a core component of Marxism, scientific socialism, and the communist movement from the very beginning in contrast to other studies of political economy and philosophy of the time (and today!) because Marxism seeks to explain and analyze why society is the way it is and how to make it better by understanding the only observable, testable universe we know of: the universe of material things and their relationships that we live within. This stands in contrast to, for example, liberal political philosophy which holds that capitalism is just the natural, most advanced, and final state of society that humans were always inherently going to create. In other words, capitalism is just a fact of reality and a natural idea that humans have discovered and that it's this idea that is responsible for creating capitalist society.
"but I just don't see what part of it requires belief in an objective world of matter."
that's not what materialism means, at least in marxist therm. materialism means humans facts are dependent on space and time, so to say. so, the relationships of productions, are historically connoted and situated in space. that's why we are materialists. historical materialists.
we reject idealism: we don't believe that culture is the engine of history, for example. we reject all forms of idealism, we reject the "idea" of state (for example), the state for us is a product of the relationships of production . we believe material relationships of production are the engine of history.
that's a very synthetic answer. but the point is: materialism is not primarily concerned with physical objects or "things." Instead, it centers on the intricate interplay of historical and spatial contexts in shaping human realities.