Philosophy of Being and Knowledge

Philosophy of Science

Karl Popper's Critical Rationalism

The most prominent critic of the neopositivist theory of science was the Austrian-British philosopher Sir Karl Raimund Popper (1902-1994), whose position he termed critical rationalism. Popper challenged the concept of verification, arguing that no amount of collected facts could ever verify a scientific theory. For example, no matter how many black ravens scientists observe, they can never prove the truth of the theory that all ravens are black. Popper believed that science operates by a different method: scientists do not seek to prove theories as absolute truths; rather, they create working theories. These theories need only function effectively in explaining the world, not be unquestionably true.

In practice, this unfolds as follows: A scientist begins with an intriguing idea, evaluates whether it is logical and aligns with common sense, and then tests the hypothesis through observation or experiment. If the theory seems to work in a few instances, it is presented to the scientific community, where others will also test it. Based on several instances, a conclusion is drawn about the likelihood of the theory’s validity, and it is accepted in science. However, everyone understands that the theory may not be true, since proving its truth would require testing every possible case, which is impossible. No one can observe every raven that has ever existed to confirm they are all black, yet it would be unreasonable for humanity to refrain from calling ravens black just because of this. A few hundred observed ravens suffice to establish a working theory. Similarly, although it is impossible to test the electrical conductivity of every piece of copper, it would be foolish to stop using copper in industry.

There are no scientific statements that can be empirically verified in the strict sense of the term. Science, therefore, operates with probabilistic theories—those that work in practice rather than being empirically provable truths.

The likelihood of a scientific theory is not static; it fluctuates over time. Each use of a theory affects its probability. For instance, the more black ravens people see, the higher the probability that the theory claiming all ravens are black is correct. Yet even after observing many black ravens, one cannot claim the theory is proven true. However, should even one white raven be discovered, the theory would be falsified. Popper called this refutation process "falsification." He argued that while no number of positive facts can verify a theory, a single negative fact is enough to falsify it, rendering it obsolete.

Popper also rejected the neopositivist concept of meaningful statements. While neopositivists believed that only empirically verifiable statements hold truth value, Popper demonstrated that no such statements exist in science. Hence, if only verifiable statements were deemed scientific, science itself would be rendered impossible. Popper introduced a different criterion: scientific statements are those that can be criticized. For example, anyone can test the theory of black ravens at any time by seeking to falsify it. This means the theory is scientific because it is open to criticism. In contrast, Marxism-Leninism, the dominant ideology in the USSR, was not scientific, as it was forbidden to critique it. Criticizing this ideology led to severe punishment by the Soviet authorities. Thus, Popper divided statements into two types: scientific and non-scientific, with the possibility of criticism serving as the demarcation line between science and other forms of knowledge.

The inability to critique a scientific theory may stem not only from political power but also from objective circumstances. Popper cited the example of ancient atomists, who claimed that the world was composed of atoms—indivisible particles. At the time, there were no technical means to test this claim through experience, making it impossible to critique. As such, ancient atomism could not be considered scientific, although it played a significant role in inspiring future scientists to explore the components of the world, eventually leading to the modern atomic theory in physics. Thus, while ancient atomism was unscientific, it was still beneficial to science.

These examples led Popper to abandon the neopositivist concept of statements devoid of truth value. History shows that certain theories, which could not be empirically tested for truth in the past, were later proven true. Therefore, the development of science is a continuous interaction between three realms. Popper called the first world the objective reality—the world science investigates. The second world is the realm of human perceptions, the subjective picture of the world for each individual. The third world is the world of science itself. The subjective world shapes the world of science, while the objective world refines it by eliminating false perceptions.

Popper's theory of science became the foundation of his political philosophy. Just as only those theories that are open to criticism are scientific, so too are only those political systems that can be freely criticized politically virtuous. In democratic societies like the UK or the US, citizens are free to criticize their rulers, meaning these societies are open. In contrast, in North Korea, where citizens cannot criticize their leader, society is closed.