Sherlock Holmes often told Watson that he used deductive reasoning when he came up with a conclusion. He believed it, but that doesn’t change the fact that he was wrong. He used inductive reasoning. Dr. Greg House, the modern, medical version of Holmes, made the same mistake.
Deductive reasoning is fairly simple to explain. A + B = C. You have certain facts that, when combined, have only one possible conclusion. Math uses deductive reasoning. So does computer language. As I mentioned last week, this is where you’ll find proof.
When there is more than one possible conclusion. You have to come up with the most likely of all possibilities. This is inductive reasoning. When House put a list of what diseases where most likely for a patient, then crossed off the ones that couldn’t be the case, he was looking for the most possible solution, not the only solution. You saw that with the number of solutions that were wrong. If they were the only possible answer, they would have been correct. This doesn’t mean that the conclusion has the possibility of being wrong. The evidence can be so overwhelming the conclusion could be set in stone. An example would be that for every day that humans could observe it, the sun rose in the east. Therefore tomorrow, the sun will rise in the east. Technically, not a forgone conclusion, but the evidence in way too strong to say anything else and not sound stupid.
For inductive reasoning, you need both quality and quantity of evidence. There is no set equation for what to look for, it’s up to the thinker to determine, but basic human reasoning will limit the conclusions. That was my design. Anyway, quality tends to trump quantity; if the evidence is good or bad enough it doesn’t matter how much of it you have. Take the sun example above. If all you had was the observation as evidence, that’s not a lot of evidence. But it’s really good, so it’s enough. But if you see a rock with a letter “C” on it, no picture of stars, and a flag waving, as well as a multitude of other evidence, and came up with the conclusion that man hasn’t been to the moon, all the evidence would come from a lack of understanding of how certain things work in the world and thereby bad evidence, so you would easily come up with the wrong conclusion.
Often, it takes both ways of thinking, even if it relies mostly on inductive reasoning, to figure something out. This is mostly an if-then scenario. If A is one thing and B is another thing, then A + B = C. You would use inductive reasoning to determine A and B, then the conclusion is based on deductive reasoning. However, since the factors are determined by inductive reasoning, there is no proof.
Next week, I’ll go into the difference between knowledge and truth. See you then.