For Karl Marx, fundamental concepts of social justice were rooted in economic justice. For Marx, economic inequality, and the existence of private property, resulted in social injustice. One particular concern of his was that when ownership was separated from the means of production, and work from the final product (e.g. a worker who simply uses a machine that makes a small part for a car rather than working on a car as a whole) workers become alienated and unhappy. Thus social justice has two parts. One is "from each according to his abilities and to each according to his needs" -- people doing the work for which they are best suited and all people having their economic needs supplied. The second part is workers owning the means of production and restructuring work so that workers can feel connected to and get emotional satisfaction from their labour.