The creation of the proletariat was the result of the destruction of the feudal system in Europe; with the breakup of the feudal manor, the former peasant was dispossessed of his income-producing property and turned out of his village. As a "free" man, he now had nothing to trade but his labo. Since a proletarian has no means of survival other than trading his labor for money ( = working at a job), then he is at the mercy of the capitalist, who owns and controls the means of production by which value is created.
The existence of a proletarian class is the basis for both capitalism and communism; in a capitalist state, property is owned by capitalists (i.e. those few who own and control capital), who exchange their money for the labor of those who have nothing but their labor to sell (the proletariat). In time, free competition by capitalists in an open market eventually drives the price of everything (including labor) down to its natural price (of which slavery is the ultimate end) while those who control capital (and ths are not dependent upon wages) remain unaffected. Under communism, the state (i.e. those who own and control the state security apparatus) controls the means of production directly, and exchanges their money for the the labor of those who have nothing but their labor to sell (the proletariat). In time, government-mandated wage and price controls diverge so radically from reality that an immense black market forms, reduucing the workers to an equality of poverty (of which slavery is the ultimate end) while those who control the State (and thus are not dependent upon wages) remain unaffected.
In both cases, the mass of the population are reduced to mere economic units, powerless to control their own destiny. In a capitalist economy, capital and credit are increasingly centralized into the hands of a few, incestuous monooply groups; under communism, capital and credit are increasingly centralized into the hands of the State bureaucracy and security apparatus.
Over time, this centralization will destroy the productive capacity of the society, creating a depression. Under a capitalist system, workers in a depression have no jobs, no money, and do not spend; under a communist system workers in a depression have "pretend" jobs and "pretend" money, but nothing to spend it on. In both cases, an angry dispossessed, hungry, and increasing desparate population is created. When the situation becomes bad enough, the proletarians decide "they have nothing to lose but their chains" -- and chaos results.
In a capitalist society, the proletarians in revolt seize capital and the state security apparatus by force and declare a communist state; in a communist socitey, the proletarians destroy the state, and thus abdicate power to whatevever ethnic faction, crime syndicate, or warlord is able to establish local dominance. In both cases, ruin is the ultimate end.
Belloc points out that a man with political freedom but no property (capital) is not free at all; he is an economic slave, at the mercy of the man who employs him. This is why, in Belloc's view, what we call capitalism ought rightly to be called "proletarianism", since it depends upon the existence of a propertyless class (the proletariat) for its own existence. In the Catholic view, any system in which most men are slaves is unjust. Since the problem on both capitalist and communist societies is the concentration of capital into a few hands, the solution therefore is to distribute capital as widely as possible, giving every man a means of survival that does not rely on the whim of another.
This system of Catholic political economy is called Distributism, and it is I believe well worth looking into.
Let us consider a hypothetical. Let's assume that the world is newly created. There are "x" amount of people and "x" amount of resources that can be evenly divided in a way that is just (ie= equal). In this system, nobody is a proletariat because nobody has an advantage over anyone else- ie nobody is an economic slave. Will this model hold over time? In other words, after a century or so, will everyone still possess all their capital or equal amounts of capital?
That question is the crux of the problem. How you answer it defines your political leanings.
Also, the black market economy must be factored into the Marxist model. There is no way to circumvent the black market. It follows totally rational rules (from a human behaviour standpoint). It is an expression of the amount of control exerted by the State upon economic affairs and free will.
It is absurd to suppose that communism and capitalism are cousins. Capitalism will exist independent of human intervention in human economy- ie the black market. No amount of control will circumvent this result. Indeed, control is the impetus for the black market.
But communism and its concepts (ie- proletariat) is a totally human creation which has no basis in reality. It has never been demonstrated to work in a satisfactory manner whereas the black market always exists and operates under a well understood framework. The black market is the economy operating in the absence of economists or control by politicians.
Communism, on the other hand, can simply not operate over the long term. It relies upon capitalism. Capitalism was seen as the precursor to communism by Marx. It could not happen before capitalism was developed to "such and such" point. It logically follows that if capitalism never develops to "such and such" point communism can never happen even though capitalism is constantly in existence.
There is no rational basis to suppose that capitalism and communism are two fruits from the same tree. Communism essentially is theft. Theft cannot happen until there is something to steal. I will not equate a producer of wealth with an absconder of wealth but I fully understand that some people seek to. Given certain circumstances (outside human morality) it must appear easier to simply appropriate wealth than to go to the trouble to produce it. This is what our earthly struggle is all about.
Capitalism or the black market will function regardless of the political circumstances and regardless of the given resources. Communism can only function once a certain amount of assets have been accumulated to steal.