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All ravens are black. Yep. The question is, how do you prove this?

The scientific method amounts to:

  1. Make observations
  2. Form an inductive hypothesis
  3. Experimentation to confirm or refute
The problem is, to prove the hypothesis, one has to observe as many ravens as possible, and confirm that they are all black. It is impossible to observe every raven - many of them have died, many of them haven't existed yet, and there could be ravens in inaccessible locations. However, each time we see a black raven, it tends to confirm the hypothesis that all ravens are black.

Yet, there is a part of this that is missing - only one side of the test has been performed. A -> B is equal to its contrapositive: not B -> not A. "If its a raven, then it is black" is equivalent to "if its not black, then it is not a raven". Therefore, every sighting of a non-black non-raven equally confirms the hypothesis. The red coffee cup on your desk is helping prove that all ravens are black.

Yes, it is silly, but by the laws of logic, if you accept an inductive hypotheses and confirmation by experiment, then every observation except the one that refutes the hypothesis confirms it - no matter how irrelevant.