|Karl R. Popper, The Logic of
Scientific Discovery (Basic Books, Inc., New York, 1959), p. 278.
...Science is not a system of certain, or well-established, statements;
nor is it a system which steadily advances towards a state of finality. Our science is not
knowledge (episteme): it can never claim to have attained truth, or even a
substitute for it, such as probability. ...
Ibid., p. 280.
The old scientific ideal of episteme--of absolutely certain,
demonstrable knowledge--has proved to be an idol. The demand for scientific objectivity
makes it inevitable that every scientific statement must remain tentative for ever.
It may indeed be corroborated, but every corroboration is relative to other statements
which, again, are tentative. Only in our subjective experiences of conviction, in our
subjective faith, can we be `absolutely certain'....
Ibid., p. 281
...Science never pursues the illusory aim of making its answers final,
or even probable. Its advance is, rather, towards the infinite yet attainable aim of ever
discovering new, deeper, and more general problems, and of subjecting its ever tentative
answers to ever renewed and ever more rigorous tests.
Francisco J. Ayala in Evolution by Theodosius
Dobzhansky, Francisco J. Ayala, G. Ledyard Stebbins and James W. Valentine (W.H. Freeman
and Co., San Francisco, 1977), p. 476.
Seeking the systematic organization of knowledge and trying to explain
why events are as observed are characteristics that distinguish science from common-sense
knowledge. However, these characteristics are also shared by other forms of knowledge,
such as mathematics and philosophy. The characteristic that distinguishes the empirical
sciences from other systematic forms of knowledge is that scientific explanations must be
subject to the possibility of empirical falsification. Falsifiability is indeed
the criterion of demarcation that sets science apart from other forms of knowledge
(Popper, 1934). A scientific hypothesis (or theory) must be empirically testable. A
hypothesis is tested by ascertaining whether or not precise predictions derived as logical
consequences from the hypothesis agree with the state of affairs found in the empirical
world. A hypothesis that is not subject to the possibility of rejection by observation and
experiment cannot be regarded as scientific.