Surprising, exceptional cases — so-called black swans — can provoke extraordinary change in the way we do things or conceptualize the world. While it is not unreasonable to be surprised by a black swan, to be surprised by subsequent cases that are similar enough that they might cause the same sort of upheaval is unforgivable. The problem is how to reason about these almost novel, not totally unforeseen, subsequent cases that I call gray cygnets.