It would seem that socialist ideology has the ability to stamp widely separated or even historically unlinked socialist currents with indelible and stereotyped markings.

It seems to us quite legitimate to conclude that socialism does exist as a unified historical phenomenon. Its basic principles have been indicated above. They are:

The manifold embodiments of these principles are linked organically by a common spirit, by an identity of specific details and, frequently, by a clearly discernible overall thrust.

Our perspective on socialism takes into account only one of the dimensions in which this phenomenon unfolds. Socialism is not only an abstract ideological system but also the embodiment of that system in time and space. Therefore, having sketched in its outlines as an ideology, we now ought to be able to explain in what periods and within what civilization socialism arises, whether in the form of doctrine, popular movement or state structure. But here the answer turns out to be far less clear. While the ideology of socialism is sharply defined, the occurrence of socialism can hardly be linked to any definite time or civilization. If we consider the period in the history of mankind which followed the rise of the state as an institution, we find the manifestations of socialism, practically speaking, in all epochs and in all civilizations. It is possible, however, to identify epochs when socialist ideology manifests itself with particular intensity. This is usually at a turning point in history, a crisis such as the period of the Reformation or our own age. We could simply note that socialist states arise only in definite historical situations, or we could attempt to explain why it was that the socialist ideology appeared in virtually finished and complete form in Plato's time. We shall return to these questions later. But in European history, we cannot point to a single period when socialist teachings were not extant in one form or another. It seems that socialism is a constant factor in human history, at least in the period following the rise of the state. Without attempting to evaluate it for the time being, we must recognize socialism as one of the most powerful and universal forces active in a field where history is played out.

Igor Shafarevich
The Socialist Phenomenon, p. 200

See also: Abolition of the family (at Fathers for Life)