Science vs. Pseudoscience

Similarities

• Both claim to be valid, predictive models of how nature works.
• Both tend toward jargon. Jargon always sounds official and impressive to those who don't know the jargon, which enhances the mystique and aura of power of both science and pseudoscience. Furthermore, similar jargon is used in both. For example, "energy." For a scientist or engineer, energy is measured in joules, (or calories, ergs, kilowatt-hours (=3.6 million joules), or British thermal units), and is an extremely useful quantity because it is conserved, which means that it can be put into different forms, but never created or destroyed. In pseudoscience the term energy is also used frequently, but a pseudoscientists "energy" is seldom, if ever, the same energy as used by a physicist. Instead, the pseudoscientist's energy is undefined or ill-defined, and is used with equal emphasis in such different contexts as the "energy" felt by a dowser looking for water, the "energy" exuded by the planets that astrologers tell us influence our lives, the "Chi energy" of Chinese spirituality, or the psychic energy concentrated in crystal balls. In pseudoscience, energy is an unknown agent that must be present in order to affect the material world, but whose nature is not known.

Differences

• I think the most definitive distinction between science and pseudoscience is that science is falsifiable but pseudoscience is unfalsifiable. Science is arranged so that any incorrect hypothesis will be exposed and corrected if it conflicts with experiment. Secure theories like special relativity have had hundreds of experimental confirmations over the years, and some of special relativity's predictions like time dilation test to extremely high accuracy every time they are tested. Pseudoscience is arranged so that any deviations from its predictions are readily explained within the internal logical precepts of the pseudoscience itself. Example: most modern astrologers reject total determinism. Rather than saying that the positions of the planets at birth determine personality and fate, they assign some weight to free will. ("The stars incline, the do not compel." See question 14 in the astrology FAQ.) In the event that a horoscope is perceived as inaccurate, and other excuses fail, acts of free will can always explain the inaccuracy. Another example: It is impossible to discount UFO sightings at the 100% level. It is clear that 90% are easily explained as obvious hoaxes or as sightings of other natural or man-made phenomena. With more work, about half of the remaining sightings can also be explained. This leaves about 5% of UFO sightings that are inconclusive. Even if the UFO community agreed with these statistics, which they don't, it is still possible for UFOs to exist because only one sighting has to be a real extraterrestrial.
• There is also a distinct sociological difference. For unproven hypotheses science operates by encouraging investigation and communication between scientists, both informally and formally through publications of results in technical journals. An individual scientist will accrue a good reputation by definitively disproving a hypothesis. Eventually, consensus by the whole community is reached. Pseudoscience is far less critical of itself, and individuals are not rewarded for attacking portions of pseudoscientific dogma. There is less of a community, and unproven hypotheses are seldom investigated.
• Science is reductionary, pseudoscience fractionary. Most scientists are driven by the urge to explain the universe with a set of simple models, the simpler the better. The desired end is one model, understood by everybody. Pseudoscience may make similar claims, but in fact pseudoscience practice is distinctly individualistic and does not drive toward a single model. Instead, a tolerance toward related pseudosciences exists, and a sense of "different paths toward one goal." This means that, without a mechanism for pruning dead branches, pseudoscience is prone to endless schisms. Thus, astrology can be either sidereal (Vedic), tropical, natal, electional, mundane, horary, medical, meteorological, Chinese 12-year, or millenial. (From this source.) Smaller pseudosciences like dowsing are completely individualistic and thus have no drive toward unity.
• The application of scientific experimental methods to pseudoscience topics have never resulted in conclusive proof. This has resulted at least in the fact that neither scientists nor pseudoscientists have strong desires to begin more testing. Scientists because the past negative results are so strong as to indicate a very small probability that further tests would be positive, and pseudoscientists for much the same reason. An unfortunate side effect is that scientists tend to laugh at pseudoscience. I think that this is wrong. Pseudoscience does not work, but its psychological and sociological consequences are very important. I want mankind to reach for the stars, and I fear that the irrationality represented by the pseudoscience symptom may hold us back.