The Logic of Scientific Discovery
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Popper, K.R.(1980). The Logic of Scientific Discovery. London: Hutchinson, pp. 27-48
Def. of empirical sciences: Construction of hypothesis, systems or theories and test them against experience + experiment (p.27)
1. The Problem of Induction • Empirical sciences are inductive methods
o Singular statements turn into universal statements (results of observation) (p.27)
• But! Inductive method is not purely logical
o Accordingly, inductive inference is not strictly valid, but can bear some level of reliability (p.28)
o Reichenbach: Science does not decide upon truth or false, but rather probability (p.28)
o Author: inductive method leads to infinite regress and is not sufficient for science (p.30)
2. Elimination of Psychologism • No logical analysis needed of how a theory was invented/came to his inventor’s mind
Author makes distinction between: • Psychology of knowledge (empirical facts) vs. logic of knowledge (logic relations) (p.31)
o Questions of fact vs. questions of justification/validity
o Conceiving a idea vs. examining it logically
• What to receive with logical reconstruction/examination? -> systematic approach of analyzing • Author: there is no pure logical path, but rather, every discovery contains ‘an irrational element’ – “creative intuition” (p.32)
3. Deductive Testing of Theories • 4 ways to test a theory (p.33)
o Compare conclusions with one another (internal consistency)
o Investigation of the logical form (empirical or scientific or tautological?)
o Compare with other theories
o Empirical application of the conclusion
• Compare with practical results of experiments
o Either positive (verified) or negative decision (falsified)
o If positive, only temporarily, because subsequent might be negative -> decision overthrown
• Author wants to replace inductive with deductive method
4. The Problem of Demarcation o Critique: rejecting inductive method means removal of barrier between science and speculation o Author: inductive methods do not provide a sufficient distinction o “the problem of inductive methods consists in asking for a logical justification of universal statements about reality, (…) because there are not genuine statements” (p.37)
5. Experience as a Method o Def. of empirical science (p.39)
o Synthetic (must represent a possible world)
o Fulfill criteria’s of demarcation (possible experience)
o System has to be proven by experience (deductive method)
6. Falsifiability as a Criterion of Demarcation o Theories have to be empirically verified or falsified!
o Test them with experience
o Author: (since dismissing inductive methods) “theories are, therefore, never empirically verified!” (p.40) o Therefore: A negative result will give the empirical truth!
o Refutation by experience (p.41)
o “Consequently, it is possible by means of purely deductive inferences (…) to argue from the truth of singular statements to the falsity of universal statements”
7. The Problem of the Empirical Basis (…) 8. Scientific Objectivity + Subjective Conviction o Usage of Kant’s understanding of Objectivity (Conviction) and Subjectivity subjective causes of judging) (p.44) o Objectivity of scientific statements is closely connected with the construction of theories (p.44) o Only through rules, regularities and repetition, we can test them! (p.44) o Main point: a subjective experiment can never justify a scientific statement (inductive method) (p.46) o But: “systems of theories are tested by deducing them from statements of a lesser level of universality -> requires testing as infinitum!!!!!!!
o [earlier, author attacked inductive methods for leading to infinite regress]
o Only difference, here, tests are not intended to establish or justify a system (p.47)
o You cannot test forever, therefore it is important that scientific statements have the capability of being tested (p.48) o No statement has to be accepted as truth, because it is not testable (p.48)
Popper makes a clear distinction between inductive and deductive methods and their usage in empirical sciences. In his opinion, inductive collection of information only leads to subjective observations. To underline this argumentation, a practical example will help to clarify: The statement, all swans are white might be the result of experiments which were lasting for months, nevertheless, only one black swan will disprove the whole statement. Therefore, the author warns that it is not valid to turn singular statements into universal ones. Rather he dismisses all inductive methods, as a subjective experiment that can never justify a scientific statement. In the end the author has to acknowledge that both ways need to be empirically tested, whether inductive or deductive. The only major difference, he claims, is that the deductive method does not intend to justify or establish a theory. His last sentence might display his motivation: The call for more critical reflection, towards statements that used to be accepted as truth, although they could not even be tested! Hempel underlines the importance of cause and effect and because of that he states that history can formulate general laws. The main difference, therefore, is the perspective of the two authors. Whereas Popper rejects inductive methods, as subjective observations, Hempel considers history to formulate general laws, which is in complete contrast to what Popper wrote. One could argue that Popper uses ‘a negative method’, as he says only negative results can prove. On the other hand, Hempel seems to pursue a positive method, as he believes that singular statements can turn into universal ones, accordingly he uses the inductive method. Concerning Popper, I have to admit that even though his line of argumentation is reasonable, I would disagree that inductive methods are not part of science. The question of whether to start with the theory first or with ‘subjective observation’ is not the point of discussion, rather both have to be acknowledged as scientific methods for empirical research. However, one should always avoid generalizations.
