No particular theory may ever be regarded as absolutely certain.... No scientific theory is sacrosanct.
Karl PopperA theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.
Karl PopperThere is no history of mankind, there is only an indefinite number of histories of all kinds of aspects of human life.
Karl Popper