Changes

=== Falsifiability ===

=== Falsifiability ===

In his seminal work, ''The Logic of Scientific Discovery,'' Karl Popper repudiated induction, and proposed the bright line of [[Falsifiable|falsifiability]] as a demarcation between science and non-science.  In order to be scientific, a theory must be testable, and the results of the testing must either corroborate the theory, or falsify it.  A proposed theory is falsifiable, if it is conceivable to conduct an experiment that would disprove the theory.  For example, Newton's law of gravity was a valid scientific theory because it is falsifiable; that is, the Law of Gravity is experimentally testable, and a measurement taken that violates Newton's law would falsify it, while a measurement that substantiates the theory would corroborate it.

In his seminal work, ''The Logic of Scientific Discovery,'' Karl Popper repudiated induction, and proposed the bright line of [[Falsifiable|falsifiability]] as a demarcation between science and non-science.  In order to be scientific, a theory must be testable, and the results of the testing must either corroborate the theory, or falsify it.  A proposed theory is falsifiable, if it is conceivable to conduct an experiment that would disprove the theory.  For example, Newton's law of gravity is a valid scientific theory because it is falsifiable; that is, the Law of Gravity is experimentally testable, and a measurement taken that violates Newton's law would falsify it, while a measurement that substantiates the theory would corroborate it.

While chemistry, Newtonian physics among others are science, metaphysics and pseudoscience are not scientific. Whilst it is commonly stated that Popper believed Evolutionary Theory to be unscientific, since he argued that it was tautological in 'Unended Quest' (1976), he in fact withdrew his criticism in 'Dialectica' (32:344-346), stating;  

While chemistry, Newtonian physics, and many other fields belong to science, metaphysics and pseudoscience are not scientific. Whilst it is commonly stated that Popper believed Evolutionary Theory to be unscientific, since he argued that it was tautological in 'Unended Quest' (1976), he in fact withdrew his criticism in 'Dialectica' (32:344-346), stating;  

"I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation"

"I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation"

=== Universal Laws ===

=== Universal Laws ===

The falsifiability criterion arose as a result of Popper's analysis of the logic of universal laws.   Universal laws have a logical structure which precludes certain existential statements: universal laws are a negation of an existential proposition.  Popper's example was that of the color of swans.  The universal statement "all swans are white" implies the negative existential statement "no swans of a color other than white exist".  To verify the negative existential we would need to trawl through the universe to ensure that no non-white swan existed anywhere in time or space.  Conversely if we saw just one black swan we could confirm the existential statement "black swans exist" and refute the universal "all swans are white".   

The falsifiability criterion arose as a result of Popper's analysis of the logic of universal laws. Universal laws have a logical structure which precludes certain existential statements : universal laws are a negation of an existential proposition.  Popper's example was that of the color of swans.  The universal statement "all swans are white" implies the negative existential statement "no swans of a color other than white exist".  To verify the negative existential we would need to trawl through the universe to ensure that no non-white swan existed anywhere in time or space.  Conversely, if we saw just one black swan we could confirm the existential statement "black swans exist" and refute the universal "all swans are white".   

Popper was uncompromising in his rejection of any attempt to take confirming instances as increasing the legitimacy, likelihood, reasonableness or probability of the universal statement.  No matter how many white swans you see you are no more able to assume that all swans are white than if you had seen just the one white swan.    The ease with which “verifying” instances can be found lead Popper to the conclusion that an attempted verification of a universal law is worse than useless: to be science universal laws must be capable of being put to the test, to be falsifiable.

Popper was uncompromising in his rejection of any attempt to take confirming instances as increasing the legitimacy, likelihood, reasonableness or probability of the universal statement.  No matter how many white swans you see you are no more able to assume that all swans are white than if you had seen just the one white swan.    The ease with which “verifying” instances can be found lead Popper to the conclusion that an attempted verification of a universal law is worse than useless: to be science universal laws must be capable of being put to the test, to be falsifiable.