The cat owner Timmy has a shot gun and a cat. Every time he hears a crack of the floor, he picks up his shot gun and checks the door. It's okay; it's just his

The cat owner Timmy has a shot gun and a cat. Every time he hears a crack of the floor, he picks up his shot gun and checks the door. It's okay; it's just his cat walking around the house. But this is merely a heuristics, he thinks to himself. Being a rational person, Timmy still rushes to the door with his shot gun every time he hears a crack in the floor. The lack of sleep has invited boldness to his head, but at least so far, he has kept out every bugler who didn't show up to his door. The city lover Mary and Susan live in a city, by a busy road. There is a crossing, with proper traffic lights and timers. Susan crosses the road when the green light is on, because that's when all the cars whose route clashes with hers are not moving. But all of them? Mary questions. So far, Susan has been fine, but Mary is a well-informed rationalist who doesn't believe in heuristics. She looks left, and then right, and distrusting her own sense---because we all know that human vision is not 100% reliable---she looks left again, and then right again. She rubs her sore eyes, and decides to go back home. The road is too dangerous. --- Life would stop being plausible, if we always look out for the 0.001%. In some cases, the cost of not trusting heuristics is low, but then, that heuristics would be quite useless. Some experts work on the 0.001% case and they are warranted to be paranoid; but even then, their alertness can only be confined to a narrow application. Everything else in life is still based on heuristics.