The theory of societal differentiation dominates the ongoing sociologi
cal debate about the modernization of societies. This theory is insuff
icient if it is interpreted as a theory about the process of moderniza
tion as a whole. As a result numerous attempts are being made to defin
e the idea of modernization more sharply and to enrich it by including
aspects previously disregarded. These attempts do not, however, go fa
r enough. For this reason the article proposes adding a further theme
from the area of sociological and socio-philosophical thought, which i
s also of great significance. Up to now this tradition has been seen a
s alternative theory to the theory of societal differentiation. It is
proposed that the sociological view of social modernization in the the
ory of societal differentiation be developed by the integration of the
model of a market ordered society which draws on both liberalism and
Marxism.