The “means of production” (which may be defined, roughly, as consisting of capital goods minus human and financial capital), is a central concept in Marxism, as well as in other ideologies such as Distributism. The problems of capitalism, according to both Marxists and Distributists, arise from the fact that ownership of the means of production is concentrated in the hands of the few. Marxists propose to remedy these problems by having the means of production be collectively owned. Distributists want to retain private ownership, but to break the means of production up (where practicable) into smaller parts so that everyone will have a piece (if you wanted to describe the difference between the Marxist and Distributist solutions here, it would be that Distributists want everyone to own part of the means of production, whereas Marxists want everyone to be part owner of all of it).
Where a society’s economy is based primarily on agriculture or manufacture, thinking in terms of the means of production makes some sense. In an agricultural economy wealth is based primarily on ownership of land, and in a manufacturing economy ownership of things like factories and machinery plays an analogous role. In a modern service-based economy, by contrast, wealth is based largely on human capital (the possession of knowledge and skills). As Pope John Paul II notes in Centesimus Annus, “[i]n our time, in particular, there exists another form of ownership which is becoming no less important than land: the possession of know-how, technology and skill. The wealth of the industrialized nations is based much more on this kind of ownership than on natural resources.”
Human capital, however, is not only explicitly excluded from the means of production by definition, it cannot be easily fitted into a similar framework. Unlike land or machinery, human capital cannot be easily alienated from the individual, either to another individual or to the collective as a whole.
The unalienable nature of human capital ought, I think, to cheer those of a Distributist perspective, as it approximates by analogy the widespread ownership of land or machinery that Distributists sought. At the same time, the increasing importance of human capital to the economy makes the means of production a concept with diminishing significance, as prosperity and economic security become less dependent on owning land or other sorts of physical productive goods.