Karl Popper's Philosophy: Falsifiability and the Nature of Scientific Theories
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Scientific theories can be clearly distinguished from all other theories in that they bear a special mark – falsifiability. Said Popper: Any scientific theory could be shown to be false if some conceivable observation were true. Popper argues that the Baconian/Newtonian insistence on the primacy of ‘pure’ observation, as the initial step in the formation of theories, is completely misguided: all observation is selective and theory-laden.
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Popper, then, repudiates induction, and rejects the view that it is the characteristic method of scientific investigation and inference, and substitutes falsifiability in its place. It is easy to obtain evidence in favour of virtually any theory, and such ‘corroboration’, should count scientifically only if it is the positive result of a genuinely ‘risky’ prediction, which might conceivably have been false. For Popper, a theory is scientific only if it is refutable by a conceivable event. Every genuine test of a scientific theory is logically an attempt to refute or to falsify it, and one genuine counter-instance falsifies the whole theory. Popper’s theory of demarcation is based upon his perception of the logical asymmetry which holds between verification and falsification: it is logically impossible to conclusively verify a universal proposition by reference to experience, but a single counter-instance conclusively falsifies the corresponding universal law.
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Every genuine scientific theory is prohibitive, in the sense that it forbids, by implication, particular events or occurrences. It can be tested and falsified, but never logically verified. Thus Popper stresses that it should not be inferred from the fact that a theory has withstood the most rigorous testing that it has been verified; While advocating falsifiability as the criterion of demarcation for science, Popper explicitly allows for the fact that in practice a single counter-instance is never sufficient methodologically to falsify a theory, and that scientific theories are often retained even though much of the available evidence conflicts with them… Scientific theories arise genetically in many different ways, and the manner in which a particular scientist comes to formulate a particular theory may be of biographical interest, but it is of no consequence as far as the philosophy of science is concerned.
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Popper stresses in particular that there is no unique way, no single method such as induction, which functions as the route to scientific theory, a view which Einstein personally endorsed with his affirmation that ‘There is no logical path leading to [the highly universal laws of science]. They can only be reached by intuition… Science, in Popper’s view, starts with problems rather than with observations – it is, indeed, precisely in the context of grappling with a problem that the scientist makes observations in the first instance: his observations are selectively designed to test the extent to which a given theory functions as a satisfactory solution to a given problem.
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Popper claimed scientific beliefs are universal in character, and have to be so if they are to serve us in explanation and prediction. For the universality of a scientific belief implies that, no matter how many instances we have found positive, there will always be an indefinite number of unexamined instances which may or may not also be positive… A single negative instance is sufficient to prove that the belief is false, for such an instance is logically incompatible with the universal truth of the belief.
