Chapter 2 Falsifiability

Chapter 2: Falsifiability Bejamin Rush and Yellow Fever: Yellow fever epidemic of 1793 in Philadelphia: Benjamin Rush was a doctor (and signer of the Declaration) who treated it. He subscribed to the theory of the day that illness accompanied by fever should be treated by bloodletting. We now know that bloodletting is a dangerous practice. Rush, however, became even more confident in the practice after the epidemic was over, even though some of his patients died. Why? Because he had the attitude of believing that each success (patient who lived) was attributable to bloodletting. If they died, it was merely testament to the severity of the disease. This is a problem of falsifiability. Rush’s approach would’ve made somewhat more sense if he had attributed the successes to bloodletting but considered the deaths as evidence contradicting bloodletting. But he rationalized away the disconfirmations—a fatal error in science. He made it impossible to falsify his theory. Falsifiability criterion. Scientific theories always must be stated in such a way that predictions derived from them can be potentially shown to be false. This is the falsifiablity criterion. The Falsifiability criterion states that for a theory to be useful, its predictions must be specific. In telling us what should happen, the theory must also imply that certain things will not happen. If those certain things that will not happen actually happen, it means that the theory may be flawed or may need to be modified. Either way, it’s a win-win situation because we end up with a theory that is nearer to the truth. In contrast, if a theory does not rule out any possible observations, then the theory can never be changed and we are stuck in our current way of thinking with no possible way to move forward. **A successful theory is NOT one that accounts for every possible happening because such a theory robs itself of any predictive power. The phrase “it’s only a theory” is a misconception because it implies that the theory is worthless and is merely a hunch. A theory is much more than that. Specific vs. Precise Imagine that your colleague tells you he can guess who is knocking at your office door based on the rhythm of the knock. The first time someone knocks, he tells you that he predicts it will be a female knocking. You open the door and find a female. You’re only mildly impressed because he had a 50% chance of being correct. The next time someone knocks, he says it will be a male under 22 years of age. Indeed it is, so you are a little bit more impressed, but only slightly since you’re on a college campus and there are many males under the age of 22. Hoping to truly impress you, he then tells you Thinking Straight about Psychology that the third person knocking is a 30-year-old woman who is 5’2” tall who is carrying a book and purse in her left hand and knocking with her right.” When you open the door to find he was right, you are extremely impressed. Why are you more impressed with the third case? Because the hypothesis was specific and precise and could have been falsified more easily. (There were more chances that he could’ve been wrong.) The greater the specificity of the hypothesis, the greater their impact when they are confirmed because they had greater chances of falsification. “Progress occurs only when a theory does not predict everything but instead makes specific predictions that tell us—in advance—something specific about the world. The predictions derived from such a theory may be wrong, of course, but this is a strength, not a weakness.” “A new theory has to explain all of the facts that the old theory could explain PLUS the new facts that the old theory could not explain. So the falsification of a theory does not mean that scientists have to go back to square one.” 5