Karl Popper’s criterion of Falsifiability

Throughout his academic career, Karl Popper (1902-1994) had to defend himself from being branded a ‘positivist’ as he was on an altogether different path from the Vienna ‘logical positivists’ (including Wittgenstein) and their search for a criterion of ‘meaningfulness’, that is a clear demarcation between ‘sense’ and ‘non-sense’. In this respect, the positivist quest was purely ‘linguistic’ whereas Popper’s was a purely ‘scientific’ one.
For the latter, the ‘positivist’ quest was a mistake as every time we attempt to define a scientific term – or otherwise – the definition ends up being circular. Why? because we have put ourselves under the obligation to introduce new ‘terms’ which themselves have to be, in their turn, defined and scrutinised and so we are launched into an infinite regress with no hope of clarifying the matter at hand but, on the contrary, with the genuine risk of complicating it. For Popper, the important issue was not to clearly distinguish between ‘sense’ and ‘non-sense’ but with what, at bottom, constituted ‘science’ and ‘non-science’.
It is a waste of time for philosophers to get bogged down in the logical dissection and analysis of ‘words’ while neglecting to clarify what constitutes ‘scientific activity’. Popper’s enemies were neither ‘religion’ nor ‘religious belief’ but Marxism and Psychoanalysis and their alleged scientific claims. To the Austrian philosopher of science, they were nothing more than ‘pseudo-sciences’ as none of their claims could actually be put to the ‘falsifiability’ test. They were not a (scientific) ‘matter of fact’ but ‘a matter of faith’ and for that reason, were mere ‘ideologies’.
‘To count as scientific theory, a theory must be empirically testable and since the only form of testing that is logically possible is falsification, this means that only statements that are empirically falsifiable can have scientific status.’
For Popper, knowledge is essentially a human construct and consequently can never claim to be, in any sense, objective, timeless or incorrigible. At best, it is ‘what we have the best grounds at any given time for believing.’ After all, Newton’s laws were THE received explanation for the natural laws of physics until questioned and proved partly ‘falsifiable’ through Einstein’s discoveries in his Special and General Theory of Relativity. Newton’s Laws were regarded as the ‘absolute’, ‘incorrigible’ paradigm of science for over two hundred years … until the beginning of the twentieth-century. Contemporary scientists have begun to speculate about the possible existence of sub-atomic particles, ‘neutrinos’, travelling at a speed higher than light itself, thus ‘putting to the test’, the claims established by Einstein and a century of quantum science. Contrary to religious beliefs, scientific ones are open to constant challenges from dissenting voices and counter-evaluations are always welcome in the light of new hypotheses and experiments. How can religious beliefs achieve any level of ‘falsibiality’ when their foundations are timeless, eternal and ‘incorrigible’? Isn’t ‘falsifiability’ a pipe dream to all those who, Christians and Muslims alike, try and adapt the most traditional religious practices to the modern world and bring a new, more flexible understanding and knowledge of their faith?