Habermas's philosophical account of communicative reason is one thing. His sociological account of what goes wrong in modernity is another, and the two come together in the concept of the colonization of the lifeworld, which is his most politically precise diagnostic concept.
The lifeworld (Lebenswelt, borrowed from Husserl and given a social dimension) is the background horizon of shared meanings, norms, and communicative practices within which everyday interaction takes place. It is what we take for granted when we communicate: the shared language, the common stock of cultural knowledge, the norms of social coordination, the personal identity formations shaped by family and community. The lifeworld is reproduced through communicative action, through the ongoing processes of reaching understanding, achieving social solidarity, and forming personal identities through interaction with others.
The system refers to the subsystems of capitalist economy and state administration, which are coordinated not through communicative action and shared understanding but through steering media: money (for the economy) and power (for the administration). The economic system does not need participants to agree about values or understand each other. It coordinates behavior through prices, incentives, and contracts. The administrative system coordinates through legal norms, bureaucratic procedures, and official authority. These are, in a limited domain, legitimate and efficient. The expansion of market economies and democratic states is not itself pathological.
The pathology, which Habermas calls the colonization of the lifeworld, occurs when the steering media of money and power penetrate domains that should be governed by communicative action. When the family is reorganized around economic optimization rather than solidarity. When the educational system is redesigned to produce efficiently trainable workers rather than to cultivate communicative competence and critical thinking. When healthcare relationships are restructured around cost-efficiency rather than patient-care norms. When political discourse is replaced by the strategic management of public opinion by spin operations and media management. In each case, something that should be coordinated through shared understanding and mutual recognition is instead being colonized by money or administrative power.
This is more precise than Adorno's diagnosis. Adorno condemned instrumental reason as such. Habermas's diagnosis is targeted: some domains appropriately use instrumental rationality (market coordination, administrative regulation), and others do not. The crisis of modernity is not that reason is inherently dominating but that the boundaries between the system and the lifeworld have been systematically violated. The IEP notes that this gives Habermas a more optimistic political conclusion than the first generation: since the pathology is not intrinsic to reason itself but to the distortion of the boundary between communicative and strategic action, the response is institutional, rebuilding the conditions for genuine communicative action in the domains that have been colonized, rather than the total critique of modernity that Adorno's position seemed to require.