马克思对工人阶级（working class）的理解不是狭义的。他不认为只有做蓝领工作的才算工人阶级。他提出了“现代工人阶级（modern working class）”的概念。这个版本中Introduction的作者Marshall Berman详细解读了一下现代工人阶级的含义。他先引用了一段马克思的原话：
[T]he modern working class, developed -- a class of labourers, who live only so long as the find work, and who find work only so long as their labour increases capital. These labourers, who must sell themselves piecemeal, are a commodity, like every other article of commerce, and are consequently exposed to all the vicissitudes of competition, to all the fluctuations of the market.引自 Introduction
然后Berman解读道：
The crucial factor for Marx is not working in a factory, or working with your hands, or being poor. All these things can change with fluctuating supplies and demands in technology and politics. The crucial reality is the need to sell your labor in order to live, to carve up your personality for sale, to look at yourself in the mirror and think, 'Now what have I got that I can sell?' and an unending dread and anxiety that even if you are okay today, you won't find anybody willing to buy what you have or what you are tomorrow; that the changing market will declare you (as it has already declared so many) worthless; that you will find yourself physically as well as metaphysically out in the cold.引自 Introduction
Out in the cold。作者还是很温和了。他要是把这句话补完，应该是这样：Out in the cold and starving to death.
所以这才是我，或者说我们绝大多数人，内心焦虑的来源。这也是为什么proposal时K问的那个问题"how are you going to find a job?"能让我顿那么长时间都没办法回答（因为无法回答，没有答案）。都说“日光下无新事”。一百多年前马克思早就看到了，我们都是工人阶级，无论以什么形式存在。
表示其中内容是对原文的摘抄
