The Lagoon TechMy little blog in Cyberspace.

This logical fallacy is known as “black and white”. This is when someone suggests only two alternative conclusions are possible for a certain situation. However, several possibilities exist, not just two of them.

For example, Amanda woke up sick with a cold. Her friend Lilly tells her either she slept with the A/C on all night (as she usually does) and caught the cold that way, or she caught the cold from someone at work. While this generally is not a big deal, what Lilly did was technically a logical fallacy.

Amanda could have caught the cold from someone at the store. She also made several trips to the post office delivering packages. She could have caught it from someone there. She also has art class. She could have contracted the cold during one of the lessons she attended. Lilly is aware of all these facts, but she still insists only the two possibilities she mentioned can be true.

Also, what if a doctor did the exact same thing? He only investigates “two possible reasons” why you are sick. However, there are potentially a dozen or more reasons why you may be sick, but he only investigates the “two possible reasons” instead? Unless he has a good reason for ignoring the other possibilities, that would not be very good, would it?

Summary: Saying only two possibilities exist to explain why something happened, when there are many possibilities, is not wise. It is best to give all possible alternative conclusions when trying to figure out an issue to avoid possible trouble.