Human nature
The human nature argument is used by capitalist apologists and is relatively popular due to bourgeois anti-communist propaganda and misconceptions about Marxism.
The premise of the argument is that human nature is greed and self-interest, thus socialism will never work because people are greedy and inherently self-interested. This argument is deeply flawed and lacks any material analysis or reference to history. The greed mentioned is the result of capitalism's failure; where if you are not "greedy," you will be driven bankrupt, homeless and potentially starve. This argument also falsely applies the values of the capitalist ruling class on the majority of the population, who must be greedy and maximize their profits by exploiting the majority of the human population (the working class).
The human nature argument is also premised on a metaphysical understanding of history. According to proponents of this argument, human nature is inherently predisposed to a capitalistic mentality of extreme individualism and self-interest despite capitalism only existing for roughly 200 years, entirely omitting tens-of-thousands of years of pre-capitalist human activity. For instance, human interacted with each other in a radically different manner during primitive communism relative to the present.
Socialism will eliminate the need for greed or self-interest, as it guarantees every human housing, a job, and freedom, thereby allowing them to be altruistic.