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Popper's philosophy หลังจากหายไปนานกลับมาอีกครั้งพร้อมกับอาจารย์ของ โซรอส

Philosophy of Science
Popper coined the term critical rationalism to describe his philosophy. This designation is significant, and indicates his rejection of classical empiricism, and of the observationalist-inductivist account of science that had grown out of it. Popper argued strongly against the latter, holding that scientific theories are universal in nature, and can be tested only indirectly, by reference to their implications. He also held that scientific theory, and human knowledge generally, is irreducibly conjectural or hypothetical, and is generated by the creative imagination in order to solve problems that have arisen in specific historico-cultural settings. Logically, no number of positive outcomes at the level of experimental testing can confirm a scientific theory, but a single genuine counter-instance is logically decisive: it shows the theory, from which the implication is derived, to be false. Popper's account of the logical asymmetry between verification and falsification lies at the heart of his philosophy of science. It also inspired him to take falsifiability as his criterion of demarcation between what is and is not genuinely scientific: a theory should be considered scientific if and only if it is falsifiable. This led him to attack the claims of both psychoanalysis and contemporary Marxism to scientific status, on the basis that the theories enshrined by them are not falsifiable. His scientific work was influenced by his study of quantum mechanics and by Albert Einstein's approach to scientific theories. Popper's falsificationism resembles Charles Peirce's fallibilism. In Of Clocks and Clouds (1966), Popper said he wished he had known of Peirce's work earlier.
In All Life is Problem Solving (1999), Popper sought to explain the apparent progress of scientific knowledge—how it is that our understanding of the universe seems to improve over time. This problem arises from his position that the truth content of our theories, even the best of them, cannot be verified by scientific testing, but can only be falsified. If so, then how is it that the growth of science appears to result in a growth in knowledge? In Popper's view, the advance of scientific knowledge is an evolutionary process characterized by his formula:
PS1→TT→EE→PS2
In response to a given problem situation (PS1), a number of competing conjectures, or tentative theories (TT), are systematically subjected to the most rigorous attempts at falsification possible. This process, error elimination (EE), performs a similar function for science that natural selection performs for biological evolution. Theories that better survive the process of refutation are not more true, but rather, more "fit"—in other words, more applicable to the problem situation at hand (PS1). Consequently, just as a species' "biological fit" does not predict continued survival, neither does rigorous testing protect a scientific theory from refutation in the future. Yet, as it appears that the engine of biological evolution has produced, over time, adaptive traits equipped to deal with more and more complex problems of survival, likewise, the evolution of theories through the scientific method may, in Popper's view, reflect a certain type of progress: toward more and more interesting problems (PS2). For Popper, it is in the interplay between the tentative theories (conjectures) and error elimination (refutation) that scientific knowledge advances toward greater and greater problems; in a process very much akin to the interplay between genetic variation and natural selection.
In his earlier work Conjectures and Refutations (1963), Popper abandoned his previous rejection of the idea that truth is not a particularly relevant goal for science to pursue. He adopted the semantic theory of truth formulated by the logician Alfred Tarski in 1948. According to this theory, the conditions for the truth of a sentence as well as the sentences themselves are part of a metalanguage. So, for example, the sentence "Snow is white" is true if and only if snow is white. Although many philosophers have interpreted, and continue to interpret, Tarski's theory as a deflationary theory, Popper explicitly refers to it as a theory in which "truth" must be replaced with "corresponds to the facts."
He bases this interpretation on the fact that examples such as the one described above refer to two things: assertions and the facts to which they refer. He identifies Tarski's formulation of the truth conditions of sentences as the introduction of a "metalinguistic predicate" and distinguishes the following cases:
1) "John called" is true.2) "It is true that John called."
The first case belongs to the metalanguage whereas the second is more likely to belong to the object language. Hence, "it is true that" possesses the logical status of a redundancy. "Is true", on the other hand, is a predicate necessary for making general observations such as "John was telling the truth about Phillip."
Upon this basis, along with that of the logical content of assertions (where logical content is inversely proportional to probability), Popper went on to develop his important notion of verisimilitude. In words, the intuitive idea behind verisimilitude is that the assertions or hypotheses of scientific theories can be objectively measured with respect to the amount of truth and falsity that they imply. And, in this way, one theory can be evaluated as more or less true than another on a quantitative basis which, Popper emphasizes forcefully, has nothing to do with "subjective probabilities" or other merely "epistemic" considerations.
The simplest mathemical formulation that Popper gives of this concept can be found in the tenth chapter of Conjectures and Refutations.. Here he defines it as:
where Vs(a) is the verisimilitude (or truthlikeness) of a, Ctv(a) is a measure of the content of truth of a, and CTf(a) is a measure of the content of the falsity of a.
Knowledge, for Popper, was objective, both in the sense that it is objectively true (or truthlike), and also in the sense that knowledge has an ontological status (i.e.–knowledge as object) independent of the knowing subject (Objective Knowledge: An Evolutionary Approach, 1972). He proposed three worlds (see Popperian cosmology): World One , being the phenomenal world, or the world of direct experience; World Two , being the world of mind, or mental states, ideas, and perceptions; and World Three, being the body of human knowledge expressed in its manifold forms, or the products of the second world made manifest in the materials of the first world (i.e.–books, papers, paintings, symphonies, and all the products of the human mind). World Three ), he argued, was the product of individual human beings in exactly the same sense that an animal path is the product of individual animals, and that, as such, has an existence and evolution independent of any individual knowing subjects. The influence of World Three, in his view, on the individual human mind (World Two) is at least as strong as the influence of World One. In other words, the knowledge held by a given individual mind owes at least as much to the total accumulated wealth of human knowledge, made manifest, than to the world of direct experience. As such, the growth of human knowledge could be said to be a function of the independent evolution of World Three. Compare with Memetics. Contemporary philosophers have not embraced Popper's Three World conjecture, due mostly, it seems, to its resemblance to Cartesian dualism.