By SHIDARTA (June 2026)
Two major philosophers, Karl Popper (1902–1994) and Jürgen Habermas (1929–2026), both introduced the terminology of “three worlds” into their philosophical discussions. Although they worked within different intellectual contexts, their shared terminology is itself worth exploring. Because both distinguish three worlds, readers might assume that they propose similar frameworks. This short article compares their ideas and considers the relevance of that comparison to legal philosophy.
Karl Popper developed his theory within epistemology and the philosophy of science. His central concern was how knowledge can be objective even though it initially arises from human mental activity. Jürgen Habermas, meanwhile, developed his concept of three worlds within his theory of communicative action. His primary concern was not the ontological status of knowledge, but the conditions that enable people to reach mutual understanding through rational communication. Thus, whereas Popper sought to explain the structure of reality in which knowledge exists, Habermas sought to explain the structure of communication through which claims concerning knowledge, norms, and subjective experience can be exchanged and justified.
During the 1990s, a vigorous debate known as the “Positivism Dispute” (Positivismusstreit) took place. The term “positivism” is itself misleading because the opposing sides actually represented two critical traditions: critical rationalism and critical theory. Both explicitly challenged the positivism of the Vienna Circle and that of Comte. Neither side, therefore, represented positivism. Karl Popper can be associated with critical rationalism, although he was no longer directly participating in the debate. Critical rationalism was represented primarily by Hans Albert, while critical theory was represented by Theodor W. Adorno and Habermas, both associated with the Frankfurt School. The debate centered on whether the social sciences should follow the methods of the natural sciences or adopt different methods because their subject matter consists of human beings and society. This article will not explore the Positivism Dispute in detail, but Popper’s and Habermas’s respective positions help clarify their different philosophical backgrounds.
Popper held that reality is not confined to a single domain. He sought to understand its ontological structure and accordingly divided reality into three distinct but interacting worlds. World 1 is the world of physical objects and material events. World 2 is the world of subjective experience, including consciousness, perception, emotions, and individual mental states. World 3 is the world of the objective products of human intellectual activity, such as scientific theories, mathematical systems, language, literary works, institutions, and legal norms.
Popper’s principal contribution lies in his idea that human intellectual products can acquire a relatively autonomous existence once they have been created. A scientific theory, for example, no longer depends entirely on its creator. Subsequent generations can criticize, improve, or develop it. In this sense, World 3 is an objective world distinct from both the material world and individual consciousness. Knowledge is no longer understood as someone’s mental state, but as an object that can be publicly accessed, tested, and debated.
Unlike Popper, Habermas developed his concept of three worlds as part of his theory of communicative action. His starting point was therefore not an inquiry into the ontological structure of reality. Instead, he focused on the worlds referred to in communication and on how communicative rationality operates in social life. According to Habermas, every communicative act implicitly refers to three worlds. First, the objective world consists of facts and states of affairs about which claims can be assessed as true or false. Second, the social world consists of norms, institutions, and expectations governing relationships between individuals. Third, the subjective world consists of individuals’ personal experiences, intentions, and feelings. When people speak, they simultaneously raise claims relating to these three worlds. Statements about facts raise claims to truth; statements about norms raise claims to normative rightness; and statements about personal experience raise claims to truthfulness or sincerity.
Despite emerging from different theoretical traditions, the two theories share several points of convergence. Both reject materialist reductionism, which holds that reality consists solely of physical objects. Both Popper and Habermas recognize a subjective dimension that cannot be reduced to material processes alone. They also recognize a dimension that extends beyond individual experience and makes social life and the development of knowledge possible. Nevertheless, these similarities should not obscure their fundamental differences. Popper’s theory is ontological because it addresses the question of what exists. Habermas’s theory, by contrast, is pragmatic and communicative because it addresses how people understand one another and justify the claims they raise in social interaction. Popper’s World 3 therefore cannot be equated directly with Habermas’s social world. World 3 encompasses all objective products of human intellectual activity, including scientific theories, mathematics, and law, whereas Habermas’s social world refers specifically to the normative dimension governing social relationships.
I would now like to bring this comparison into legal philosophy. The two theories’ different orientations give them different uses in this field. Popper’s theory helps explain the ontological status of legal norms. More precisely, the ontology of his three worlds helps explain the possibility of objective knowledge, including knowledge concerning legal norms. Legal norms can be situated within World 3 as intellectual products that acquire an objective and relatively autonomous existence once formulated. A norm is not identical to the physical document containing it—which is why World 3 is sometimes viewed as a virtual representation of World 1—but neither is it identical to its creators’ mental states. It can still be interpreted, criticized, and applied long after its creators have died. From this perspective, law is understood as an object of knowledge with an intersubjective existence that can be studied scientifically. Such an outlook would make it impossible for Popper to accept the argument that “legislation is beyond challenge.”
Habermas’s theory, on the other hand, helps explain how legal norms acquire legitimacy and how legal argumentation proceeds. In judicial practice, judges do not encounter legal norms merely as abstract objects. They must also assess the facts of a case, interpret the relevant norms, and consider the parties’ claims. These elements relate to Habermas’s three worlds. The facts of a case refer to the objective world: factual claims must be justified as true. The validity of norms refers to the social world: normative claims must be justified as right. The parties’ good faith refers to the subjective world: subjective claims must be shown to be sincere. Habermas’s theory therefore provides a more suitable framework for understanding justification in legal discourse, specifically how a claim can be justified. “Justification” is thus a key term in his approach.
We might suspect that Popper would be uncomfortable with this term. In his view, no amount of evidence obtained through induction can establish a universal theory. Yet justification would require a universal theory. A thousand observations may support a theory, but a single anomaly may be enough to undermine it. For Popper, the search for justification often leads to dogmatism. Once people believe they have found a certain foundation, they tend to stop criticizing.
This is where Habermas enters the discussion effectively. Popper successfully showed that no theory can be justified conclusively. If a theory loses its potential to be falsified, it falls outside the domain of science. Habermas, however, would promptly ask: “If there is no final justification, how can society reach collective normative decisions?” In science, we might be inclined to respond that justification remains available as long as a theory has not been refuted.
The central issue, then, is not whether certain truth exists. This also extends to the existence of justice or utility, both recurring concerns in legal philosophy. Habermas seeks to redirect our attention. Rather than asking about certain truth, we should discuss justification that participants in discourse can rationally accept. From Habermas’s standpoint, this leads to the most crucial question: the quality of the justificatory procedure itself.
Habermas is certainly concerned with this issue. He therefore introduces an ideal model of communication—the ideal speech situation—through deliberative processes and a political system of deliberative democracy. In this situation, all participants in discourse are assumed to be free to speak, and every argument has an equal opportunity to be examined. Many criticisms have been directed at this ideal, which some philosophers regard as too far removed from reality, or counterfactual. Habermas, however, is well aware of the difficulties encountered in the real world, particularly in countries where democracy still develops through trial and error.
Let us return to this article’s central idea and consider where Popper and Habermas converge and diverge. Hypothetically, Popper would agree with Habermas on the importance of open discussion, rational criticism, freedom of expression, opposition to dogmatism, and the rejection of authorities immune to criticism. However, Popper would not go as far as Habermas in making the quality of deliberative procedures the basis of normative legitimacy. Whereas Habermas emphasizes that legal norms acquire legitimacy through inclusive, rational procedures of discourse free from domination, Popper would emphasize that every claim, decision, or institution must remain open to criticism, testing, and revision. Habermas thus focuses on legitimacy through discursive justification, while Popper focuses on freedom through unending criticism.
The comparison between Popper’s and Habermas’s three worlds therefore suggests that the two theories complement rather than replace one another. Popper provides a framework for understanding law as part of the objective world of human intellectual products possessing a relatively autonomous existence. Habermas provides a framework for understanding how law operates in social communication through claims to truth, normative rightness, and sincerity. In legal philosophy, Popper’s theory is therefore better suited to explaining the ontology of legal norms, while Habermas’s theory is more relevant to explaining the rationality of legal argumentation and the legitimacy of law. Used together, they offer a fuller understanding of law as both a system of knowledge and a discursive practice within social life and legal practice. (***)
This article is a translation from: https://business-law.binus.ac.id/2026/06/14/tiga-dunia-popper-dan-habermas-dan-relevansinya-bagi-filsafat-hukum/
