On leaving the door to the unknown open....

All scientific knowledge is uncertain.  This experience with doubt and uncertainty is important.  I believe that it is of very great value, and one that extends beyond the sciences.  I believe that to solve any problem that has never been solved before, you have to leave the door to the unknown open.  You have to permit the possibility that you do not have it exactly right.  Otherwise, if you have made up your mind already, you might not solve it. 

-Richard P. Feynman,  The Meaning Of It All:  Thoughts of a Citizen-Scientist