Science and pseudoscience
You have been trying to formulate ways of distinguishing between scientific disciplines, such as astronomy, and pseudoscience such as astrology. One difference between the two that you might have noted, is that science typically makes (i) concrete predictions that (ii) can either succeed or fail, whereas pseudosciences typically do not. To see this, consider again the caes of astronomy and astrology.
Astronomy will make concrete predictions about, a future solar eclipse. For instance, astronomers may predict that there will be a solar eclipse on a certain date and time. And clearly, that sort of prediction is testable: we can see whether a solar eclipse does indeed take place on that date and time. If it does, the prediction will have been successful. If it does not, the prediction will have failed.
Zodiac woodcut from the sixteenth century. Via Wikimedia Commons
Matters are different, however, when an astrologer comes up with a horoscope that tells you that ‘something special will happen to you in the next few weeks, even though it might go unnoticed to you and your environment’. The prediction here is vague (‘something special’ is vague, and ‘the next few weeks’ is not very specific either). Also, even though this prediction might succeed (if something special does indeed happen to you in the next few weeks), it is hard to see how it might fail. After all, if you find that something special has indeed happened to you, it will have succeeded. But if you don’t notice anything special, it won’t have failed either. After all, it says that the special event that it predicts ‘might go unnoticed to you and your environment’. The way in which the prediction is formulated, then, immunises it against critique.
In the words of the Austrian philosopher of science, Karl Popper (1902-1994), it cannot be ‘falsified’, or shown to be wrong. According to Popper, it was a hallmark of scientific claims that they can, in principle, be falsified. Pseudoscientific claims, like the claims made in horoscopes, often cannot.
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