Popper's Critical Rationalism consists of two parts: 1) a critical attitude towards science; 2) a critical attitude towards politics. The critical attitude towards science meant that he regarded all scientific knowledge as fallible. No certainty exists in science. All scientific theories are subject to severe tests and are constantly facing the evidence. This is his famous method of falsifiability: all scientific knowledge is fallible. When he applies to it politics, it turns into the fallibility of political leaders and their ideas. It becomes his plea for an open society, in which the rule of law guarantees that political ideas and programmes are subject to rigorous scrutiny to prevent political leaders from doing too much harm. In an open society, the individual enjoys inalienable rights.

Literature:

Popper, K.: Conjectures and Refutations (1963)

Popper, K.: Objective Knowledge (1972)

Popper, K.: The Open Society and Its Enemies (2 volumes, 1966)

Popper, K.: Unended Quest - An Intellectual Biography (1976)

Weinert, F.: Karl Popper - Professional Philosopher and Public Intellectual (2022)