Albert Einstein: Why Socialism? http://coto2.wordpress.com/2010/05/15/albert-einstein-why-socialism/

If we ask ourselves how the structure of society and the cultural attitude of man should be changed in order to make human life as satisfying as possible, we should constantly be conscious of the fact that there are certain conditions which we are unable to modify. As mentioned before, the biological nature of man is, for all practical purposes, not subject to change. Furthermore, technological and demographic developments of the last few centuries have created conditions which are here to stay.

In relatively densely settled populations with the goods which are indispensable to their continued existence, an extreme division of labor and a highly centralized productive apparatus are absolutely necessary. The time — which, looking back, seems so idyllic — is gone forever when individuals or relatively small groups could be completely self-sufficient. It is only a slight exaggeration to say that mankind constitutes even now a planetary community of production and consumption.