The Watchmaker: my fav argument

[Angrboda]

Truly, the theories that "All swans are white" and "All swans are black" both validly describe the world correctly for appropriate definitions of black and white.  

I'm not sure I understood your analogy, but I would be careful not to confuse theories with descriptions. The phrase All swans are X doesn't function as a theory.

I believe you are mistaken. It is a perfectly good theory that explains the evidence. Just as "All electrical quantities in a circuit satisfy ohm's law" is a valid theory, so is "All swans are X." The role of a theory is to explain the evidence. Perhaps you are confusing it with, "All swans that have been observed are X." Please explain to me why you feel it is not a valid theory. Theories are necessarily descriptive, so the dichotomy you propose is not correct.