Changes

Popper came to notice the main difference between Marxism, psychoanalytic theory, and Einstein’s theory of relativity, is that a principle of falsifiability is inherent to Einstein’s theory. In contrast, he found that theories like psychoanalysis and Marxism were insusceptible to refutation or experimental falsification. In his view this made theories like these pseudo-scientific, since tests which could falsify them were inconceivable.

Weimar culture and a lineage of philosophers such as Thomas Hobbes, George Berkely, and Wittgenstein, who provided epistemological theories of sense-data, influenced the Vienna Circle’s nominalist and essentialist theories. The logical positivists held metaphysics as meaningless, consisting of nonsensical pseudo-propositions. Popper came to disagree with logical positivist theory and its fundamental claims, such as Rudolph Carnap’s position that probabilities of truth in general synthetic claims could be assessed by calculating the certainty of individual corroborating observations. Popper opposed Carnap’s reductionist position on the verifiability of universal synthetic claims largely on the basis of the Quine-Duhem thesis, which maintains that no individual theory, test, or observation can be separated from the taxonomy of thought which produces it. To Popper, an openness to being refuted by observation, testing, and criticism, was the criteria of demarcation for a claim of scientific value.

|Major Contributions=Popper proposed that an openness to falsifiability for general synthetic claims determined their scientific value. Popper therefore made the normative assumption that individual corroborations for a theory should be open to criticism and the general claim always open to refutation regardless of the probability of verisimilitude attributed to the general claim and its corroborating evidence.

Popper proposes that the empirical content of competing theories should first be compared for their degrees of falsifiability. The theory with more daring consequences, due to higher risk of falsification, contains more scientific value. According to Popper, this value is attributed because falsifiable theories have greater chance of resulting in further conjectures due to openness to refutation and therefore revision. If a critical experiment result corroborates predicted expectations, its value is taken as an encouragement to continue with the theory. But corroborations should not be taken as an element of proof for the verifiability of the theory and the unobservable. In case of a falsifying experimental result that stands against the prediction, we decide to consider the theory falsified, but only tentatively. Further consideration of how deeply the refutation effects the universal theory should lead to conjectures which might save the programme, or form a new theory to supersede the previous one. 


Günter Wächtershäuser compares Popper’s critical rationalism with the metaphor of a carriage drawn by two horses: “The experimental horse is strong, but blind. The theoretical horse can see, but it cannot pull. Only both together can bring the carriage forward. And behind it leaves a track bearing witness to the incessant struggle of trial and error”. Popper’s theory is therefore received by some as a positive method for scientific thought, a normative guide for the demarcation of sciences from non-sciences, and for progress of the sciences in general.

|Criticism=There were two waves of reception for Popper’s Logic of Scientific Discovery. The first was from the publication of Logik der Forschung in 1934. Much early criticism of Popper’s anti-inductivism came from logical positivist philosophers such as Rudolph Carnap, Otto Neurath, and Hans Reichenbach. Neurath maintained that the principle of induction is unsound, but that Popper did not sufficiently show why a falsified theory should be discarded and not the falsifying evidence. Hans Reichenbach likened dismissing inductivism from scientific method as reducing the process of discovery to ‘divination’. This kind of criticism holds that induction is not a problem for science, but is essential in developing and testing theories.

The return of criticism and interpretation of Popper’s work was due to the English publication of Logic of Scientific Discovery. Many arguments took over the vein of criticism from members of the Vienna Circle: that Popper’s rules for theory choice and scientific rationality represented an ideal of research, which was too distant from the actual practice of science. Wesley C. Salmon, a pupil of Reichenbach’s, Imre Lakatos, and Joseph Agassi, who studied under Popper, all held that Popper’s anti-inductivism and non-justification of theories by corroborations were ambiguous.