“Our connection to reality is never just perception. It's always theory-laden. Scientific knowledge isn't derived from anything. It's like all knowledge. It's conjectural, guesswork, tested by observation, not derived from it.”-----Karl Popper
So, were ‘testable conjectures’ the great innovation that opened the intellectual prison gates? No. Contrary to what's usually said, testability is common, in myths and all sorts of other irrational modes of thinking. Any crank claiming the sun will go out next Tuesday has got a testable prediction. Until proved, any intellectual and any simpleton has equal comportment for his declaration.
Consider the ancient Greek myth explaining seasons. Hades, God of the Underworld, kidnaps Persephone, the Goddess of Spring, and negotiates a forced marriage contract, requiring her to return regularly, and lets her go. And each year, she is magically compelled to return. And her mother, Demeter, Goddess of the Earth, is sad, and makes it cold and barren. That myth is testable. If winter is caused by Demeter's sadness, then it must happen everywhere on Earth, simultaneously. So if the ancient Greeks had only known that Australia is at its warmest when Demeter is at her saddest, they'd have known that their theory is false.
What was it that made this explanation false....its the testability, the scientific contemplation. If there is some defecting in any story that you are told (not just a logical defect....any bad explanation), what does that mean? As David Deutsch said, “Explanation is an assertion about what's there, unseen, that accounts for what's seen.”
The myth of Persephone’s forced marriage might appear poise with the logic of weather cycle...or it might appear so at the first glimpse but it fails on the scientific balance....because the explanatory role of the marriage can be replaced by infinitely many ad-hoc explanations. Why a marriage contract and not any other reason for regular annual occurrence? Here is one. Persephone wasn't released. She escaped, and returns every spring to take revenge on Hades, with her Spring powers. She cools his domain with Spring air, venting heat up to the surface, creating summer. That accounts for the same phenomena as the original myth. It's equally testable. Yet what it asserts about reality is, in many ways, the opposite.
This easy variability is a precursor of bad explanations. Until you have some strong reason to prefer any one variable over many others available.....your explanation is bad. Good explanations can’t be easily varied while still explaining the phenomenon. Our explanation of seasons connecting the earth’s tilt and sun’s inclination is a good one....because every detail in there has a functional importance and ‘hard to vary’.
Now if the Greeks would have discovered that seasons in Australia are out of phase, they could have easily varied their myth to predict that. For instance, when Demeter is upset, she banishes heat from her vicinity, into the other hemisphere, where it makes summer. But altering their theory wouldn't have got the ancient Greeks one jot closer to understanding seasons, because their explanation was bad ‘easy to vary’. If the axis-tilt theory had been refuted, its defenders would have had nowhere to go. No easily implemented change could make that tilt cause the same seasons in both hemispheres.
This ever-redolent quest for hard-to-vary theories is the basis of all progress. Two approaches blight progress. One is easy-to-vary theories and the other is explanation-less theories. If you told about some occurrence or phenomenon unarmed with a hard-to-vary explanation....its just like they’re telling you that a wizard did it.
When you are told that carrots have human rights because they share half our genes -- but not how gene percentages confer rights -- wizard. When someone announces that the nature-nurture debate has been settled because there is evidence that a given percentage of our political opinions are genetically inherited, but they don't explain how genes cause opinions, they've settled nothing.
That the truth consists of hard to vary assertions about reality is the most important fact about the physical world. It's a fact that is, itself, unseen, yet impossible to vary.—Bertrand Russell
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