Rejection of the personal aspect of knowing, or the subjective element, leads to an exaggerated emphasis on objectivity -- a desire for a level of certainty that eventually becomes self-defeating.
Objectivity is based on the assumption that synthetic statements are possible and necessary. The observer is not independent of what is observed; truth is impersonal and theory-barren. But the ground for believing in the general reliability of sense perception is not itself something sensed; it is a belief. Senses cannot always be trusted. Things are not what they seem.
But if truth is conceived as purely independent of all commitment and impersonal, then one's own choice of true/false cannot be acknowledged. This dilemma "has long haunted philosophy in the guise of the 'correspondence theory of truth.' Bertrand Russell, for example, defines truth as a coincidence between one's subjective belief and the actual facts (The Problems of Philosophy, 4th ed., 1919, p. 202); yet it is impossible, in terms which Russell would allow, to say how the two could ever coincide.
Positivism, as promoted energetically by physicist Ernst Mach in his book Die Mechanik (1883), rejected the claims of scientific theories of any inherent persuasive power, which he considered metaphysical and mystical. Scientific theories served only as convenient summaries of direct experience. Positivism culminated in the "verification principle", which stated that no proposition could be considered true, or even meaningful, unless it could at least in principle be verified by observation.
Trouble was, the verification principle itself could not be verified by direct observation. It was in fact a "metaphysical" proposition. Since there appeared to be no escape from this situation, by the 1960's positivism collapsed. It is no longer seriously advocated by philosophers.
It is now common to refer to all observations as "theory-laden". There is no general formula for the demarcation of theory and observation.
Physical theory, beginning with Newton's pioneering work, has by now achieved a sweeping unification of physical phenomena from the constituents of atomic particles to the cosmic Big Bang.
.... Yet there is something for which Newton -- or better to say not Newton alone, but modern science in general -- can still be made responsible: it is the splitting of our world in two. I have been saying that modern science broke down the barriers that separated the heavens and the earth, and that it united and unified the universe. And that is true. But, as I have said, too, it did this by substituting for our world of quality and sense perception, the world in which we live, and love, and die, another world -- the world of quantity, of reified geometry, a world in which, though there is a place for everything, there is no place for man. Thus the world of science -- the real world -- became estranged and utterly divorced from the world of life, which science has been unable to explain, not even to explain away by calling it "subjective".
True, these worlds are every day -- and even more and more -- connected by the praxis. Yet for theory they are divided by an abyss.
Two worlds: this means two truths. Or no truth at all.
This is the tragedy of modern mind which "solved the riddle of the universe," but only to replace it by another riddle: the riddle of itself.
The Significance of the Newtonian Synthesis, Alexander Koyré, Newtonian Studies (U. of Chicago Press, 1965, ch. 1, pp. 23-24).
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