However, observing that it doesn't know the telephone number and cannot infer what it is involves getting around Gödel's theorem. Because, if there is any sentence that is not inferrable, a system powerful enough for arithmetic must be consistent. Therefore, it might seem that Gödel's famous theorem that the consistency of a system cannot be shown within the system would preclude inferring non-knowledge except for systems too weak for arithmetic. Gödel's [G\"odel, 1940] idea of relative consistency gets us out of the difficulty.
Meanwhile a bear wakes up from a long sleep very hungry and heads South. After three miles, she comes across one of the activists and eats him. She then goes three miles West, finds another activist and eats her. Three miles North he finds a third activist but is too full to eat. However, annoyed by the incessant blather, she kills the remaining activist and drags him two miles East to her starting point for a nap, certain that she and her cubs can have a snack when she wakes.
What color was the bear?
At first sight it seems that the color of the bear cannot be determined from the information given. While wrong in this case, jumping to such conclusions about what is relevant is more often than not the correct thing to do.