The subject wanders all over the place. From dont contradict your elders, to learning about externalities (which weren't considered originally), to reality is

The subject wanders all over the place. From dont contradict your elders, to learning about externalities (which weren't considered originally), to reality is a great teacher...which is why "don't contradict your elders" is born of. Experience. Many people, especially those that are immature in some way, don't accept reality, which is hinted at, throughout. Being right, isn't enough to justify reprioritizing/wasting disinterested people's time - re: The head-on collision story. Take it up with the Textbook author, rather than pretending that taking it out on some poor physics teacher is virtuous.