I've learned to be very cautious about what we know--both in physics and in biology. That leaves me open to what I call "blue sky thinking"--considering the impossible. However, considering is not the same as believing. Bottom line: the more I know, the less I understand.
Note that Joseph's example is only to make us consider--not believe--while not letting what we believe get in the way.
That was well explored in Sagan's "Contact."