In non-monotonic reasoning new knowledge can change whether something is infered to be true. Non-monotonic reasoning often uses default rules. For example, if Hoppy is a dog, and we know that dogs (usually) have four legs, then we might conclude that the statement "Hoppy has four legs" is true. However, if we later learn that Hoppy had had a car accident as a puppy and had a leg amputated, we would then need to change our reasoning and instead conclude that "Hoppy has four legs" is false.
Defined on page 40
Used on Chap. 3: pages 40, 41, 51
Also known as non-monotonic
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