Must an hypothesis be falsifiable to be scientific?

“No, after all…
  • Some clearly scientific statements are unfalsifiable

    Consider a few propositions which are clearly unfalsifiable, and yet which nevertheless are scientific:
    • Other universes exist
    • Aliens exist
    • Electrons exist

  • Some clearly scientific hypotheses regularly tolerate falsification

    Some clearly scientific hypotheses regularly tolerate falsification (especailly in the so-called complex sciences, like medicine).1 This is relevant because the these sciences are quintessentially scientific.

    • “Falsifiability is a myth. In the messy real world of observations and experiments, theories often must be modified to accommodate new evidence. Since any theory can be modified with ad hoc assumptions to agree with contradictory observations or experiments, no theory is strictly falsifiable whether it is called science or not. Criteria for judging a modification to a theory unreasonable and therefore rejecting the modification must be added for falsifiability to have any real meaning. Falsifiability is often a double standard. Politically unpopular, unorthodox, or simply new theories are demanded to be strictly falsifiable, a condition they can never meet. Accepted scientific theories are asserted to be falsifiable even though they have been and are frequently modified to explain contradictory data. The need for criteria to reject a modification to a theory as unreasonable is either denied or not mentioned, creating an illusion of certainty. These rejection criteria are not mentioned because they are often matters of fallible personal judgment and opinion. The doctrine of falsifiability offers only a mirage of certainty in distinguishing science from non-science.” [John McGowen, The Myth of Falsifiability (2000).]
    1. The idea here is that one can always make their theory falsifiable by keeping it alive with falsifiable “auxiliary hypotheses” that account for exceptions in ad hoc ways.