Karl Popper, as one of the most influential philosophers of science of the 20th century, made significant contributions to various topics such as the scientific method, theory selection, the distinction between science and non-science, probability theory, quantum mechanics, and the methodology of the social sciences. Popper's fundamental approach in the philosophy of science was that scientific theories must be falsifiable. According to him, for a theory to be considered scientific, it must be capable of being falsified through observations or experiments. In this context, he presented a science based on falsification rather than verification, offering a critical alternative to the positivist view of science.
Popper's work extended beyond the philosophy of science, making substantial contributions to social and political thought. Opposing attempts to create universal laws based on historical determinism, Popper advocated for methodological individualism and approached theories aimed at forecasting historical development from a critical perspective. His critiques of totalitarian ideologies were particularly prominent in his work The Open Society and Its Enemies (1945), in which he offered a defense of liberal democracy and individual freedoms.
One of Popper’s most significant contributions to the philosophy of science, the principle of falsifiability, provided a theoretical foundation for attempts to draw a boundary between science and non-science. His views on the progression of scientific knowledge were criticized by thinkers such as Thomas Kuhn and Imre Lakatos, paving the way for the development of alternative approaches. Nevertheless, Popper's understanding of science continues to influence contemporary philosophy of science and remains a key reference point in discussions regarding the nature of the scientific method.
For Popper, in order for a theory to be scientifically accepted, it must be potentially falsifiable. This concept forms the basis of Popper's solution to the demarcation problem between science and pseudoscience. Popper argued that pseudoscience consists of theories that, although appearing scientific, cannot be tested or falsified experimentally. This means that pseudosciences fail to undergo proper scientific testing.
Karl Popper (1902-1994) (Credit: Stanford Encyclopedia of Philosophy Archive)
The Principle of Falsifiability
Karl Popper's contributions to the philosophy of science have significantly reshaped the understanding of the testability of scientific theories and the production of theoretical knowledge. Popper proposed the principle of "falsifiability" as the primary criterion distinguishing science from other forms of knowledge. According to this principle, in order for a theory to be considered scientific, it must be potentially falsifiable by an observation. Popper emphasized that scientific theories cannot be definitively verified without leaving room for error, but they can be falsified. This perspective highlights the necessity of constantly testing scientific theories, subjecting them to continuous critique and scrutiny.
In developing the principle of falsifiability, Popper introduced the concept of "basic statements" or "basic propositions," which are essential for testing scientific theories. These basic statements are specific propositions that indicate the existence of entities in the form of "There is an X in Y." These statements have properties that can potentially contradict universal theories and play a critical role in testing scientific theories. Popper noted that these statements must meet two conditions: they must be formally singular and entity-indicating, and they must be mutually testable. Thus, basic statements can be used in scientific tests to ensure the falsifiability of a theory.
Popper's philosophy argues that it is impossible to definitively determine the truth of theories. Instead, scientific truths can only emerge by comparing theories that have been falsified with the results of tests. According to Popper, scientists should favor theories that encompass more content and exclude more falsehoods. This does not guarantee the theory's truth, but the potential for falsifying the theory is the criterion that defines its scientific nature.
The Problem of Induction
Another significant contribution of Popper to the philosophy of science is his solution to David Hume’s problem of induction. Hume argued that scientific generalizations cannot be verified solely through observations derived from specific examples. While Popper agreed with Hume's view, he pointed out that a successful prediction is not sufficient to confirm a theory. However, if a prediction is proven false, it can immediately falsify the theory. For instance, the hypothesis "all swans are white" can be falsified by a single observation of a black swan.
Popper addressed two dimensions of the problem of induction: the logical and the psychological problems. The logical problem concerns whether general laws can be verified by specific observations. Popper argued that this is not possible. The psychological problem, on the other hand, involves explaining the confidence people have that past observations will also apply to future instances. Popper noted that this confidence creates a conflict between human psychology and scientific logic, asserting that such confidence is irrational.
Truthlikeness
While Popper accepted that it is not possible to attain absolute knowledge of the truth of scientific theories, he proposed that it is possible to determine how close they are to the truth. This is explained through the concept of "truthlikeness" (verisimilitude). The degree of reality is defined as the difference between a theory's capacity to produce correct results and its capacity to produce incorrect results. Popper believed that theories with a higher degree of reality are more accurate compared to those with a lower degree of reality.
Popper’s approach suggests that scientific theories are based on a dynamic process of continuous questioning, testing, and falsification. This implies that scientific knowledge is never final or absolute but rather exists within a structure that continually evolves, developing more accurate theories through trial and error. The philosophical framework Popper created regarding the truth of scientific theories asserts that the progression of scientific knowledge is only possible through falsifiable hypotheses.
Critique of Historicism and Holism
Karl Popper made significant critiques regarding the methods used in social sciences, particularly in fields such as sociology and economics. These critiques are closely connected to his broader views in the philosophy of science and reflect his strong opposition to historicism as well as holistic approaches like social engineering. According to Popper, the fundamental aim of the social sciences is to discover the laws that determine the development of human history or to predict the historical future. However, Popper found this approach both theoretically flawed and socially dangerous. He argued that such predictions, particularly those that attempt to forecast societal and political developments, could lead to totalitarianism and authoritarianism.
Popper viewed the core mistake of historicism as the idea that human history unfolds as a single, unified process, making the application of general laws to history impossible. Popper contended that, in natural sciences like physics, the formulation and testing of theories occupy a central role. For example, the law of gravity can be tested through various observations such as planetary movements and the speeds of falling objects. However, a law that concerns the evolution of history or the future development of specific social events cannot be subjected to such tests because a historical event occurs only once, and it is not possible to predict or test similar events in the future. This argument suggests that the capacity of the social sciences to make predictions is limited, and thus the formulation of historical laws is impossible.
Another aspect of Popper's critique of historicism relates to his opposition to the concept of "utopian social engineering." This approach advocates for the creation of a comprehensive plan or design for the radical restructuring of society by the state. According to Popper, the inability to test such plans poses a significant problem. These plans aim to change the social structure in its entirety, and if the plans fail, it would be impossible to pinpoint which part was flawed. Popper argued that the lack of testability meant that social engineering would inevitably fail, and such planning would have harmful consequences for societal development.
Popper's alternative to historicism and utopian holism was an approach based on methodological individualism and situational analysis. Methodological individualism asserts that social institutions should be analyzed through the behaviors of the individuals who constitute them. Popper argued that social institutions, such as a market economy, are not based on a specific design or conscious plan but emerge as a result of the interactions between individuals. Therefore, scientific hypotheses examining the behavior of such institutions should be formulated based on individual actions. Popper's understanding of methodological individualism was developed in close association with Austrian economist Friedrich von Hayek, and both thinkers used this approach to defend liberal market economies. Both Popper and Hayek emphasized the importance of individual freedom and the market economy over state planning.
Critique of Conventionalist Views
One of Karl Popper's most significant critiques in the philosophy of science relates to the challenges that arise when addressing how basic statements are linked to experience while examining the testability of scientific theories. Popper argued that scientific theories are realistic, but he proposed no definitive solution to the issue of how to determine the truth or falsity of basic statements. He asserted that observational statements are not dogmatic and that every observation is made based on a specific theoretical framework chosen by the observer. However, for a theory to be truly testable, it is necessary to have certain knowledge about the truth of the basic statements. Popper noted that basic statements cannot be verified by experience and are instead based on conventions accepted by scientific communities.
In contrast to traditional conventionalist views, Popper argued that basic statements are determined by decisions made by scientific communities. While conventionalists claim that the universal truths of scientific theories eventually become a matter of agreement, Popper emphasized that the rejection of theories is only possible when these basic statements are accepted. This has led to various debates about whether Popper’s views are in conflict with scientific realism. If basic statements cannot be verified by a theory, it may be difficult to reconcile the theory with scientific realism.
Critiques of the Falsifiability Principle
Popper's approach to scientific methodology has been influential for many years but has faced significant critiques, which in turn have led to the development of alternative models of scientific reasoning. Many of these critiques reject Popper's understanding of falsifiability.
One of the main criticisms of the falsifiability principle concerns the role of the relationship between theory and observation. Thinkers like Thomas Kuhn and others argue that observations are not independent of theories; instead, observations are largely shaped by existing theoretical beliefs. This situation can lead to different scientists, even when observing the same phenomena, reaching vastly different conclusions. For example, Kuhn suggests that the observation results of those advocating for classical Newtonian mechanics could differ significantly from those working within a relativistic mechanical framework. Popper's views on basic statements suggest an acknowledgment of such phenomena. However, the solution Popper proposed relies on the scientific community reaching a consensus on which observations should be considered fundamental. This solution may not be particularly effective, as disagreements often arise among scientists with different theoretical perspectives. If competing theories continuously reject each other's observations as basic, it would hinder the ability of these observations to play a significant role in falsifying theories.
Another significant criticism of the falsifiability principle is that it does not accurately reflect scientific practice. Many historians and philosophers of science argue that scientists, even when their predictions fail, do not abandon their theories. In some cases, they remain committed to these theories, even when they know that these theories have been falsified, until an alternative theory can be found. This situation reveals that Popper's concept of falsifiability does not fully capture the true practices of science. For example, Lakatos (1970) argues that before Einstein, when scientists discovered a new planet that violated classical mechanics, they would have tried to explain these inconsistencies as Popper suggested. However, Lakatos points out that even if these hypotheses failed, scientists would not abandon classical mechanics because they did not have an alternative theory.
Putnam (1975) contends that the acceptance of Newtonian mechanics was not closely related to its verifiable predictions. Instead, the theory’s acceptance was based on its success in explaining previous observations, such as the orbits of planets and the behavior of tides. This contradicts Popper’s approach, as Popper would argue that accepting an unverified theory would be irrational. Hacking (1983) also states that most scientific practices do not aim to falsify or verify a particular theory. In everyday scientific work, many observations and experiments are not aimed at testing existing theories but are rather intended simply to observe phenomena.
Another point of critique concerns Popper’s understanding of verification and its role in theory selection. Popper rejects the idea that verification shows the probability of a theory being true. Instead, verification only demonstrates a theory’s past successes. However, many philosophers of science have pointed out that Popper’s understanding of verification shares similar problems with inductivist approaches. Jeffrey (1975) argues that verification is as difficult as falsification, and he suggests that Bayesian approaches are more consistent with scientific practice.
