To understand Jürgen Habermas (born 1929), you have to start with the problem he is trying to solve, because it is among the most difficult in modern philosophy: how do you criticize modernity without sawing off the branch you are sitting on?
Habermas belongs to the second generation of the Frankfurt School, he was literally a research assistant to Theodor Adorno. He absorbed their diagnosis of modern reason as instrumental reason, as a tool of domination rather than liberation. He took seriously their account of how Enlightenment rationality had produced both the administrative machinery of the Holocaust and the culture industry's manufactured consent. But he also saw, clearly, the problem that the first generation never resolved: if all reason is instrumental reason, if the Enlightenment project is simply a form of domination dressed up as liberation, then what gives critical theory any authority to make this judgment? You cannot condemn reason using reason if reason is entirely what you are condemning. Adorno and Horkheimer had used the negative dialectic to preserve the force of criticism while refusing to ground it positively. Habermas thought this was philosophically unstable and politically debilitating.
His move: the first generation had conflated two fundamentally different kinds of reason. Instrumental reason (what Habermas calls strategic action) is reason oriented toward success, achieving an outcome by manipulating the environment, including other people. This is the reason of technology, bureaucracy, and capitalism. It treats everything, including other persons, as means to ends. And Adorno and Horkheimer were right that this kind of reason has a dominating, colonizing tendency.
But there is another kind of reason, one the first generation missed or undervalued: communicative reason, oriented not toward success but toward mutual understanding. When two people genuinely try to reach agreement through dialogue, not to win, not to manipulate, but to understand each other and be understood, they are engaging in communicative action. And communicative action, Habermas argues, has its own inherent rationality, one that is not reducible to means-ends calculation and is not inherently dominating.
The key biographical detail: Habermas was born in 1929 and, as the IEP notes, belonged to the Flakhelfer generation, youth conscripted to serve in anti-aircraft positions near the end of World War II. He heard the Nuremberg trial radio broadcasts as a teenager and learned with shock what the Nazi regime had produced. The rest of his philosophical life is, in a real sense, an attempt to understand how liberal democratic civilization can be given genuine philosophical foundations that are robust enough to prevent catastrophe. Not naive optimism, but not the hopeless pessimism of the first generation either.
Quick reflection
Think of a conversation you have had recently in which the goal was not to win or manipulate but genuinely to understand someone else and be understood. What did it feel like different from an argument or a negotiation? And think about the conditions that made it possible: was it trust, time, shared commitment to honesty, something about the setting? Habermas is going to argue that those conditions are not just accidental features of a good conversation but point to something structurally important about what language and communication actually are.