Sir Karl Raimond Popper (1902-1994) is recognized as a leading 20th century philosopher and is best known for establishing a practical philosophy of science with a framework and system for accepting scientific truths.
Popper was inspired by Sir Arthur Eddington’s 1919 south polar expedition, which tested Einstein’s 1915 General Theory of Relativity. Using curved space equations, Einstein’s theory predicts that light bends as it passes objects of large mass. The solar eclipse during the South Pole expedition provided an opportunity to witness starlight (produced behind the sun) being bent toward Earth as it traveled around the edge of the sun. The well-documented polar event propelled Einstein to international stardom and changed the world’s 200-year-old perceptions of science; Newton’s gravitational force was superseded with Einstein’s acceleration in curved space-time.
After this event, Popper began questioning how other “scientists” verified and substantiated their theories and hypothesis. For example, he refuted Freud’s theories of personality disorders because he considered “confirming instances” (coincidental verification) insufficient to establish proof. Likewise, although astrology may make numerous conjectures on what will happen in the future, failed predictions are dismissed with “ad hoc” random excuses blaming (for example) the position of Jupiter in Aquarius. Both of these areas of study are rejected as pseudo-sciences because the predictions they make are not “falsifiable”.
The advancement of falsifiability as the demarcation criteria separating true scientific theory from pseudo-science was an important initiative. The scientific field was rife with conjecture and ideas positioning themselves as scientifically proven. A measurement or standard was needed. Popper stated that when a theory passes a test (achieves a prediction), the theory is not proven, but the corroboration makes the theory worthy of more testing; it becomes tentatively acceptable, but not proven. Bona fide theories, therefore, must contain genuine predictions with a level of risk worthy and capable of critical testing. Falsifiability provides an open framework where virtually all theories have the potential to be discarded if proven wrong.
Popper insists that science must progress by a series of rejected theories, and that if a theory does not contain criteria for proving itself invalid, then it must be dismissed as unscientific.