In the 2001 novelization by Arthur C Clarke, it is explained that HAL was driven insane because it was forced to hide the actual mission from the astronauts, which was against its nature.,(reply>), So like Ava, it had a corrupting scenario imposed upon it.,(reply>), @Kit Actually HAL cheated at chess before the false equipment report.,(reply>), I've read every novel of Clarke's Odyssey series.  These books are highly cherished by me.  I would love to see film adaptations of 2061: Odyssey Three and 3001: The Final Odyssey, but only if it's done by competent people who don't take liberties with the source material.,(reply>), HAL's insanity manifested as him predicting certain equipment would fail. The astronauts checked the equipment and found no sign of impending failure - this is in the movie. HAL was going schizo. In the book, this was replicated on an identical HAL on Earth - when ordered to lie, it became erratic. HAL lip read the astronauts discussing partially shutting him down because they didn't trust HAL anymore. HAL saw this as a death threat so he decided to kill them.,(reply>), Yeah it seems weird to me that "insanity" was used to describe HAL when he has no sanity, sanity being mentally healthy. I would say HAL is a computer without sanity because there is no mental dimension to HAL. He's a perfectly logical system who will function as commanded or programmed.