## Human Logic and Fuzzy Thinking

Human beings invented logic and use it every day. However, most important decisions rely on something more than the type of rigorous logic taught in math and rhetoric classes. We are required to make decisions in a world full of partial information and imperfect data. This requires a logic that takes into account information expressed by imperfect human beings concerning events about which they have less than complete knowledge.

The basics of textbook logic courses is "Boolean" logic, based on data that can take two forms: "yes" and "no." Such logic is essential in many situations. "If the traffic light is red, stop" is an excellent rule to follow when driving. Boolean logic does quite well in such situations. However, what happens when a traffic light is green or yellow? A green light quite far in the distance may provide a trained driver with enough information to know that he should slow down, as the light is likely to change before he gets there. Another driver, facing a yellow light, may wish to consider the speed, the distance to the light, the traffic conditions, and the weather, before deciding whether to stop or go.

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