This essay deals first of all with the historical process which has led to a recognition of social rights in the framework of the wider movement of fundamental rights. The roots of social rights can be traced back to the Greek and Christian philosophies and, especially, to the Age of Enlightenment, which considered them implicitly. However, it was in the 19th and 20th centuries, with the rise of socialism and social liberalism, that they became an explicit item in the panoply of basic citizenship rights. The article describes this entire process in detail, focussing on both the most relevant figures of advocates of the social rights cause, such as Hermann Heller, and the most relevant critiques put forward against the rights approach, such as those advanced by Marxist-Leninist theory. In the second part of the essay, Prof. Peces-Barba examines the concept of social rights in its meaning and in its implications. Social rights are conceived of as "credits" of the more disadvantaged toward public agencies and, if necessary, private individuals and groups. They arise as a response to those basic human needs "that hinder a person's growth as well as her/his free choice of a life project". They are therefore fundamental in that they underlay the basis of a democratic covenant. However, they can only be claimed by those who are in real need. If generalised, their deepest significance would be lost.