Closed Doors 

Consider the following quote by Richard P. Feynman "

• "I can live with doubt and uncertainty and not knowing. I think it is much more interesting to live not knowing than to have answers that might be wrong. If we will only allow that, as we progress, we remain unsure, we will leave opportunities for alternatives. We will not become enthusiastic for the fact, the knowledge, the absolute truth of the day, but remain always uncertain … In order to make progress, one must leave the door to the unknown ajar."
  — Richard P. Feynman

This should be required learning for everyone. Not only is it relevant to science, but everything from medicine to politics. Today so many things are taken as true and unquestioned until circumstances force the issue to be re-evaluated.  Waiting for circumstances is waiting for disaster.  Surely it's better to question and start investigating alternatives early on.

Our knowledge and understanding is based on observation. As our knowledge changes the way we observe changes.  As the way we observe things changes our knowledge changes.  We are a long way from reaching the end of this cycle and closing the door.