Anna Karenina principle oft quoted from Tolstoy: "all happy families are alike; every unhappy family is unhappy in its own way". Like with any complex system,

Anna Karenina principle oft quoted from Tolstoy: "all happy families are alike; every unhappy family is unhappy in its own way". Like with any complex system, there are a lot of ways for the system to fail, and the number of states considered "working properly" is much smaller.