An efficient theory of knowledge has long been considered one of the main goals and challenges of philosophical search. A significant contribution to the development of philosophical understanding of the problems of knowledge was made by Karl Popper and presented in his captivating and thought-provoking book “The Logic of Scientific Discovery” which refutes many theories that were suggested by the philosophers earlier. The essence of Popper’s book generally consists in his new theory of critical rationalism that challenged the readers with substantially new logic of scientific discovery and made implications for further insights into epistemology. Popper’s concept of critical rationalism is a coherent, internally consistent theoretical system that gives original answers to basic problems of epistemology. Therefore, “The Logic of Scientific Discovery” remains the most remarkable philosophical book of the 20th century that provoked a heated debate concerning the theory that Popper suggests.

To start with, it is necessary to point out that Karl Popper disapproved of the philosophic tendencies that used to enlarge upon the essence of scientific discoveries and the role of knowledge in them. His extremely critical attitude can be seen from the first pages of the book that are marked with the evaluation of ideas peculiar to his predecessors. However, Popper’s criticism can be justified due to the reason that “The Logic of Scientific Discovery” is overwhelmed with precision and accurateness. Before concentrating on the concept of critical rationalism, it is worth mentioning the peculiarities of Popper’s polemics with the representatives of other philosophical theories.

To be more explicit, Karl Popper lays an emphasis on the inappropriateness of Locke’s ‘new way of ideas’ as well as ‘new way of words’ that was presented by the linguists. Language analysts underpin the assumption that philosophy as such does not exist along with its problems, stating that all the existing problems relate to the linguistic usage.  Popper sharply criticizes the philosophy of the language, taking the stance that “the analysis of knowledge by way of an analysis of ordinary language—is too narrow” (p. xxxiii). The philosopher believes that the language of science does not aim at solving the most interesting problems of epistemology that relate to its advancement. Surprisingly, Popper’s criticism fails to provide the specific names of the linguists, which means that the philosopher’s response addresses their concept of linguistic usage in general. In this context, it is reasonable to provide Popper’s key point of view that can be found in the “Preface to the First English Edition” of “The Logic of Scientific Discovery.” In contrast to linguist analysts, Popper believes that at least one problem exists in philosophy: “It is the problem of cosmology: the problem of understanding the world—including ourselves, and our knowledge, as part of the world” (p. xviii). Evidently, the philosopher’s book explores the methods that may contribute to the understanding of the world, or cosmology.

In Popper’s opinion the task of the logic of scientific discovery consists in providing a logical analysis of this procedure, namely, finding the effective method is crucial in this particular context. As it has been already mentioned above, Popper’s book is generally concerned with the concept of critical rationalism and its main peculiarities. Presenting his own theory, the author sheds light on the inappropriateness of some other methods. Specifically, the philosopher argues that the inductive method fails to provide objective conclusions and is in favor of deductive reasoning. According to Popper, logical deduction is concerned with the anticipation and hypothesis in turn. However, the main reason why Popper prefers deduction to inductive method manifests itself in his explanation that “it does not provide a suitable distinguishing mark of the empirical, non-metaphysical, character of a theoretical system” (Popper, 2005, p. 11). It means that inductive reasoning is not marked with the appropriate criterion of demarcation.

Popper’s book “The Logic of Scientific Discovery” presents the method of critical rationalism in particular. Evidently, one of the most important ideas of Popper’s concept is the reflection of rationality that may be understood as a need to choose from several alternative theories the one, which seems to be the most effective. Its effectiveness is considered through the prism of all the arguments and statements related to the assumption that rationality should not be linked with reliability and the guarantees of truth or probability. Popper understand the process of learning as the process of hypothesizing and attempts to provide a new alternative theory that may be helpful in determining the nature of cosmology. Such an understanding of the learning process presupposes the inappropriateness of induction. One of the most famous remarks that Popper makes in terms of induction is his observation that “no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white” (p. 4). This remark objects to the method of induction and reveals its incongruity.

As Popper’s concept of critical rationalism reveals his ideas about the scientific discovery and the book is based on these speculations, it is reasonable to concentrate on the essence of this concept. Therefore, the concept of critical rationalism adequately reveals the development of knowledge as an approximation to the truth. Even though this approach is a far cry from dogmatism and relativism, it requires the rejection of truth, at the same time adjusting to the search for truth. Popper’s critical rationalism refers to the notion of falsifiability, which means that the concept contributes to the realization of the hackneyed truth that all the assumptions may be consequently wrong. Due to this reason, Popper suggests that different scientific objectives and conclusions should be open to discussion.

The very term of critical rationalism raises a couple of questions that generally refer to its meaning and features that tell Popper’s concept from the already existing philosophies, such as classic rationalism. In this sense, rationalism is a belief in human mind and intelligence, the belief that when shaping our perceptions of the world one have to rely particularly on mind. In the context of Popper's theory of knowledge based on reason, critical rationalism means that a person should try as much as possible to (within the time that we have to make a decision) review available to us arguments and evidence in support of and against the known alternatives thoroughly, impartially and comprehensively. Thus, a scientist should choose the most appropriate argument, at the same time being open to new facts and ready to accept them. To be more explicit, scientists should be open to rational criticism and discussion for the sake of truth, detection and removal of wrong conclusions and errors. 

Popper considers his theory as an alternative to classical rationalism and empiricism, as well as to their synthesis. One should recall that the classical rationalism and its representatives (Descartes, Spinoza, Leibniz) is a doctrine that might get accurate, reliable knowledge about the structure of reality, not based on the experience, but on pure reason itself. Another theory is that of classical empiricism. According to the teachings of empiricists, knowledge comes from the observation of certain facts to their synthesis by means of induction. Specifically, classical empiricism is the way  with the help of which scientists open all the laws of nature. Eventually both theories of classical rationalism and classical empiricism have faced obvious problems with meanings. Concerning classical rationalism, one may argue that scientists can only learn about the relationships between purely theoretical structures regardless of the reality that was created in a human mind. This ‘reality’ can be learnt by means of the theory of classical empiricism that seems more promising in this case.

Rationality, in Popper’s opinion, is not associated with any guarantees or truths of high probability. It is simply concerned with alternative hypotheses (theories). Scientists on their way to scientific discoveries weigh all the arguments ‘for’ and ‘against’, discuss their weaknesses and reach conclusions that become apparent in the above-mentioned hypotheses. However, Popper’s principle of falsifiability suggests that the hypotheses may turn out to be wrong in the course of the applied methods and further discussion. Due to this reason, scientists may reconsider their arguments, avoid previously adopted theories and replace them with the new ones. This is the basic nature of critical rationalism. To put it plainly, the term means that a scientist should be open to the acknowledgement and acceptance of his probable failures. Understanding the idea of Popper’s rationality may contribute to a simpler formulation: the reasonable ground for believing that the theory is true is to judge in the light of all the possible arguments.

In addition, as it has been already mentioned, Popper’s critical rationalism is based on the method of deduction and principle of falsifiability in contrast to verification. The principle of verification was peculiar to the existing positivism philosophies of Popper’s predecessors and failed to meet the demands of science. Supporters of positivism believed that only verified theories had the right for existence. Thus, in its weak sense, the notion of verification can be understood as the confirmation of experiences and facts. In turn, theory becomes logical of it is possible to verify it experimentally. However, as long as the critics view this idea, it seems wrong.

Instead, Popper argued that critical theory is not exposed to inductive generalizations. It encompasses guesses, assumptions, hypotheses that scientists invent in order to solve these or other cognitive problems. Knowledge does not begin with an observation, but with the problem itself. Once the scientists realized the problem – the issue of their interest – they put forward a hypothesis. Even though observation, as an important component of rational criticism, is a means of verifying a hypothesis, in Popper’s opinion, it should not take the primary position in science.

Apparently, it is impossible to verify a hypothesis. It does not matter how many facts confirm it, one may always find the one that will refute the main idea, as in the above-mentioned case with the swans. Although the majority of swans are white, it does not confirm the non-existence of black ones. The philosopher also brings into focus the term equal-chance hypothesis, which means “a hypothesis asserting that the probabilities of the various primary properties are equal: it is a hypothesis asserting equal distribution” (p. 158). Due to this reason, it is important to seek for the facts that refute a hypothesis in order to clarify the appropriateness of the argument rather than seek for the facts that confirm it.

In his book “The Logic of Scientific Discovery”, Popper mentions that the evaluation of the theory is not isolated. It means that the evaluation of a theory is carried out by means of its comparison with other compelling theories. If the scientist deals with a problem, he may face different possible solutions. The task is to select the most plausible hypothesis that will overcome the evaluation tests. This is the scientific way of explaining the development of knowledge. Scientists face problems, hypothesize, expose them to the test rational criticism (attempts to empirical falsification), select one of the hypotheses, which best withstand this test and at the same time continue testing new challenges and set new hypotheses, continuing this cycle. The detection of new problems and the emergence of new theories may force us to scientists to reconsider the old theories, previously taken for granted. 

Interestingly, it is not enough to evaluate a theory as true or false. False theories may possess a true sense – they can be more or less close to the truth. The quality of the theory is determined not only by how big is the share of its true content (compared to false), and by how great is its meaning at all. False, but interesting, rich in meaning theory (high level of generality, universality) is more important for science than true but uninteresting, meaningfully poor theory (low level of generality). Therefore, Popper denies Bacon's idea that knowledge is developed through careful graded generalizations - from certain facts to theories. Instead, he argues that the level of generality in terms of the world’s problems significantly contributes to the solutions.

Apart from the above-mentioned principles, Popper introduces to the world of science the concept of objective probability, which is the key for comparative evaluation of competing theories and the principle of falsifiability. It means that the scientist cannot be absolutely sure about the truth of a certain theory. Thus, according to Popper,

Indeed, it is impossible to decide, by analysing its logical form, whether a system of statements is a conventional system of irrefutable implicit definitions, or whether it is a system which is empirical in my sense; that is, a refutable system. (p. 61).

Karl Popper’s theory of critical rationalism is a tremendous contribution to the world of science, as nowadays scientists mainly stick to the philosopher’s viewpoint. The potential reader of academic journals that consists of the articles, may notice that Popper’s suggestions were taken into account.  Nowadays, every scientific article presents a hypothesis with an argument that is the most appropriate in the light of the problem that is under investigation. Apparently, Popper’s book “The Logic of Scientific Discovery” has become crucial for the scientists, as it has shown the right way of interpreting the problems, identifying their nature, establishing priorities, forming the hypotheses and analyzing them from all the possible perspectives. 

To sum up the foregoing, Popper’s book has shaken the world of science due to the reason that it rejected the main existing principles and philosophies that used to define the problems in the world. The philosopher rejected the theories applied by linguist analysts, as he believed that language-oriented approach was too narrow. Popper provided explanations and solutions to the problem of induction by means of laying an emphasis on the appropriateness of the deductive methods. The concept that the author of the book proposed was called critical rationalism. According to this particular concept, the scientists should choose the most favorable argument above all and form a hypothesis that can be estimated. The main message of Popper’s book is addressed to the scientists and the particular ways of how they approach the existing problems that they would like to solve. Interestingly, apart from admitting that induction fails in science, Karl Popper focused his attention on the problem of verification, at the same time suggesting the principle of falsifiability and stating that a hypothesis cannot be false or true, as these two characteristics are always present in the possible solution. Seemingly, Popper has challenged the scientific world and the philosophy in general, bringing into focus the truths that became very helpful for the scientists in their research. His book has entirely changed the logic of scientific discovery.  

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