Although he was of Jewish descent, his family converted to Lutheranism before he was born.
Popper was educated at the University of Vienna where his father was a doctor of Law.
From his father he inherited both a love of books (he left him over 12,000 volumes from his personal library) and a keen interest in the classics, philosophy, and socio-political issues all of which laid the groundwork for his future thinking.
At the University of Vienna, Popper earned his PhD with a thesis on the nature of method in psychology which qualified him to teach physics and mathematics in high school.
While he was teaching, his thesis gained the attention of a group of philosophers, mathematicians and physicists (the Vienna Circle) who were instrumental in the logical positivist movement during the 1920's and 1930's. With the group's help, he published his first book The Logic of Scientific Discovery. It was widely read and Popper was invited to lecture at universities in the United States and Great Britain.
In The Logic of Scientific Discovery, Popper
sets out the doctrine of falsificationism in which he attempts to
repudiate the classical observationalist form of scientific
method. In it he even claims to have solved Hume's 'problem of induction'.
According to Popper, the point of a scientific theory is whether it makes predictions which could in principle serve to falsify it. The more predictions a theory makes, "the better it is." He calls this falsification a response to the 'myth of induction'. Induction, as put forth by David Hume, is the method of arriving at theories, laws or generalizations by observing regularities in experience.
The problem is, however, that no number of observed cases in which some x's possess property y elicits the conclusion that all x's possess property y. Therefore this principle cannot be justified on either logical or experiential grounds.
Popper attempts to avoid the problem of induction by arguing that scientific rationality consists of the falsification of theories rather than the inductive verification of them.
Instead of generalizations being characterized as conclusions inferred from evidence, they can logically be considered conjectures. They can be tentative hypotheses on trial in "the court of experience." In this regard, Hume's problem of induction disappears because generalizations are not supported or justified by observation.
Rather, generalizations can either be refuted by experience (as when some x's are found to lack y) or continue to await further observations. Experience can never verify a theory to be true, it can only falsify it. Generalizations first come about through conjecture and are then held up to the scrutiny of experience to be refuted.
Thus, according to Popper, in experimental testing, no number of positive outcomes can confirm a scientific theory, but a single counterexample can imply it to be false. While the term 'falsifiable' does not mean something is false, it does indicate that if it is false, it can be demonstrated by observation or experiment.
Popper used falsifiability as his criterion to differentiate
between what is, and what is not, genuinely scientific.
Consequently, a theory should be considered scientific if, and
only if, it is falsifiable. Popper's falsifiablity resembled Charles Peirce's fallibilism, which he
purportedly wished to have read about earlier in his career.
As well as being known for his self-described philosophy of critical rationalism, Karl Popper was a vigorous defender of liberal democracy and a social critic. In his book The Open Society and Its Enemies (1945), Popper criticizes Plato and his idea of philosopher-kings, and in the second volume he tackles Karl Marx, the rise of totalitarianism and what should be done about it.
Ultimately, Karl Popper's influence has served to further promote debate in the philosophy of science. It also helped give rise to the works of Lakatos, Kuhn and Feyerabend.
Karl Popper remains a philosopher of considerable standing in the fields of science, social and political thought, a dedicated opponent of skepticism, conventionalism, and a staunch defender of the 'Open Society'.