Karl Popper: Biography, Thought, Contributions And Works

Karl Popper (1902-1994) was an Austrian-British philosopher, considered one of the most important and influential thinkers of 20th century philosophy. He made great contributions to natural philosophy and to that of the social sciences.

Popper’s ideas revolved around the thought that knowledge evolves from the experiences of the mind. He denied the idea that each person’s decisions were tied to predetermined past events. Therefore, he is considered a metaphysician subscribed to the ideas of antideterminism.

In addition, he managed to deliver significant contributions to various areas of political knowledge. He sought to reconcile certain ideas that shared basic principles but were not entirely similar, such as socialism and social democracy.

He opposed, through his ideas, the classical thought of philosophical branches such as inductivist thought. He also devised the bases for the epistemological philosophy known as “critical rationalism.”



Karl Popper was born in Vienna, on July 28, 1902. At the time of his birth, his hometown was considered one of the leading exponents of culture in the Western world.

The cultural environment of Vienna to which Popper was exposed was complemented by the way in which his parents raised him: through books and knowledge. Both his mother and father were people highly involved with cultural ideas, such as music, law, and philosophy.

It is believed that Popper’s parents were responsible for instilling in him a deep interest in the social and political ideas of the world, which led him to the field of philosophy .

Another very important aspect of his upbringing was Popper’s interest in music. His mother aroused his interest in the musical field, and musical creativity caused him to generate a lot of new ideas in philosophy.

In fact, the comparisons that Popper managed to make between different branches of critical and dogmatic thought are attributed to his interest in music.


As a young man, he studied at a German high school called Realgymnasium, which prepares students for their university studies. However, he did not agree with the educational standards of the teachers.

Shortly after his short stay at the Realgymnasium, he became ill and had to stay home for several months. Unhappy with his study center, he left it to educate himself at the University of Vienna in 1918.

Interestingly, Popper decided not to immediately enroll in college. Throughout 1919, he became involved with left-wing politics and this is considered to be one of the most crucial years for his training as a philosopher.

He enrolled in a school for students with socialist views and briefly became a Marxist. However, he did not agree with the ideas of the famous German thinker and abandoned the discipline of Marxism rather quickly.

He was steeped in the philosophical thought of several renowned authors for the time, such as Sigmund Freud and Alfred Adler . In addition, he was instilled in the sciences and was part of a speech that Einstein gave in Vienna, about his theory of relativity.

Professional advancements

Originally, Popper had a hard time adjusting to a single career. In fact, he spent a few years of his youth training as a cabinetmaker, before becoming a teacher in the mid-1920s.

In 1925 he obtained a diploma to teach in elementary schools. In 1929, he applied for an additional diploma, which was awarded, to teach mathematics and philosophy in secondary schools.

Then, at the University of Vienna, he did a doctorate in the psychology department of the university. There he met two of the most important psychologists in the country. One of these psychologists was Karl B├╝hler, who took a deep interest in Popper’s doctoral work.

Doctoral work

Popper’s doctoral work dealt with a study concerning human memory , a subject of which Popper already had prior knowledge.

However, Buhler convinced Popper to change the focus of his work, which became an analysis of the methodological problems of cognitive psychology. He obtained his diploma, with this job, in 1928.

This was Popper’s first work to openly criticize other psychological ideas. From this point on, he dedicated his life to the analysis of the scientific side of psychology and to the philosophical approach as regards the method used in thinking.

His ideas were in line with many of the other thinkers of the Vienna Circle, which made him dedicate his life to the study of philosophy and leave the psychological aspects behind.

It was from that moment that Popper came to be considered one of the leading analytical philosophers of the time, along with other thinkers such as Russell and Gottlob Frege.

Personal life

In 1930, he married a woman named Josephine Anna Henninger, who was known by the nickname “Hennie.” She helped him maintain his financial well-being throughout his life and also assisted him in various professional projects, acting as his assistant.

During the first years of their marriage, they both decided that it would be better not to have children. The couple stayed true to their word throughout their marriage.

Also, in 1937, he had to go to work at the University of Canterbury in New Zealand. There it remained until the end of World War II. His wife had problems adjusting to life in this country and Popper himself did not get along with his department head.

The Second War made him focus his work on social and political philosophy. He openly criticized totalitarian ideas, such as Hitler’s.


After the end of World War II, Popper moved to England to teach at the University of London. Already living in the British country, he dedicated himself to writing a large number of literary works and his reputation as a philosophical thinker increased exponentially.

Popper began to be recognized as one of the most influential social and philosophical thinkers in the world. The works he wrote – in England – are considered today as pioneering works within the field of modern philosophy.

However, beyond the recognition he was receiving on a professional level, he became quite a secluded person on a personal level.

His personality was quite aggressive towards people who did not agree with his ideas. Furthermore, the philosopher’s magnified mentality did not sit well with the people of an England that had only recently emerged from the horrors of World War II.

Beyond his personal problems, his works and works never ceased to be recognized as sources of inspiration, both within England and throughout Europe.

Last years

During his last years of life, Popper was openly criticized for the focus his studies had on science. In addition, he was criticized for the large number of works he focused on the “logic of counterfeiting.”

He worked at the University of London until his retirement in 1969. In 1965, he was knighted by the British crown, thus becoming Sir Karl Popper. After his retirement, he continued working as a writer and speaker until his death in 1994.


The main knowledge that Popper used to develop his ideas lies in the way he saw the inductive method within the empirical sciences.

According to these ideas, a scientific hypothesis can be tested by continuous observation of the same event, repeatedly.

However, some later studies by other philosophers prove that only an infinite study of these phenomena makes Popper’s theory entirely correct.

Popper used the argument of other scientists to explain that hypotheses can be determined by a falsification criterion. That is, a scientist can check the validity of his ideas by determining an exception to them. If there is no contrary to the hypothesis, it means that it is valid.

According to Popper, sciences such as astrology and metaphysics are not considered real sciences, since they do not adhere to the principles of the falsification criterion established by the thinker.

This also includes Marxist history (the ideas he himself denied) and Sigmund Freud’s acclaimed psychoanalysis.


Demarcation and counterfeiting problem

According to this Popper theory, it is possible to distinguish between a theory of an empirical science and another of a non-empirical science.

Through this method, Popper sought to determine the methodological differences between various scientific disciplines such as physics and non-scientific disciplines, such as philosophical metaphysics.

Basically, Popper said that he is able to determine which theories have scientific bases and which others have non-scientific bases, depending on the type of argument used to prove them.

In principle, the big difference is that scientific theories assure things that, in the future, can be revealed as false through tests.

On the other hand, the theories with non-scientific bases simply claim something and this cannot be determined as false, since there is no way to prove it.

One of the main ideas that Popper used to demonstrate this theory was the contrast between the ideas of Sigmund Freud’s psychoanalysis and Albert Einstein’s theory of relativity.


According to Popper, rationality is not an idea that is limited entirely to the field of empirical sciences. He simply sees rationality as a method used to find contradictions within knowledge, and then eliminate them.

From this idea, it is possible to discuss metaphysical ideas with rational principles. Some students of the philosopher even went so far as to say that all ideas can be studied within a rational context, although Popper himself never fully agreed with such theories.

The contributions to what can be considered as rational were his main bastion that shaped the ideas of his other theories.

According to Popper, traditional philosophy is affected by the fact that many authors adhere to the principle of sufficient reason. This principle ensures that everything must have a reason or cause, but Popper thinks that not all ideas (or even theories) must have a justification.

Political philosophy

His greatest contribution to political philosophy was his criticism of the ideas of historicism, through which a high importance is usually attributed to a historical period. According to Popper, historicism is the main cause by which new authoritarian and totalitarian regimes develop in the world.

Popper ensures that human thought is a factor that develops as the human race evolves, so predicting a future event using something that happened in the past is not valid.

For a society it is not possible to know what things it will know in the future in one way or another, so historicism loses validity according to Popper’s theory.

Also, a great criticism of Popper was related to his work with the leftist party during his younger years. She realized that the Marxist uprisings caused a great deal of problems within society and, furthermore, they were not oriented correctly as far as ideology is concerned.

The great problem of Marxism and one of its main contributions is the differentiation between the ideas of equality and freedom. Marxists put equality first, while Popper determined freedom as the key tool of modern societies.


Throughout his life, Popper wrote a large number of books and literary works that influenced (and influence) many philosophers worldwide. Among his most important works are:

The logic of scientific research

Written in Vienna in 1934, The Logic of Scientific Inquiry is considered Popper’s most influential work. In the book, Popper presents his ideas of falsificationism and deals with the issues of scientific probability.

The misery of historicism

Published in 1957, The Misery of Historicism is a book by Popper in which he talks about the dangers of using historicism in a political concept.

According to the philosopher, historicist ideas are dangerous and the main instigators of corrupt and authoritarian regimes.

the open Society and Its Enemies

Popper wrote this book during World War II, and it was published in 1945. In this book, he criticized philosophers such as Marx and Plato for using historicism as the basis for their philosophical ideas. It is one of his most important texts, but also one of the most criticized.


  1. Karl Popper, Stanford Encyclopedia of Philosohpy, 1997. From Stanford.edu
  2. Karl Popper, Encyclopaedia Britannica, 2018. Taken from Britannica.com
  3. Karl Popper: Philosophy of Science, Internet Encyclopedia of Philosophy, (nd). Taken from iep.utm.edu
  4. Philosophy of Science (according to Karl Popper), University of Melbourne, 2017. Taken from unimelb.edu.au
  5. Karl Popper’s Works in English, The Karl Popper Website, 2011. Taken from tkpw.net

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