Since 1998, The Edge: http://www.edge.org has hosted an annual question and answer forum with one question per year...and the questions have included: 

2001 : WHAT QUESTIONS HAVE DISAPPEARED? 

2008 : WHAT HAVE YOU CHANGED YOUR MIND ABOUT? WHY? 

2002 : WHAT IS YOUR QUESTION? ... WHY?

2013 : WHAT *SHOULD* WE BE WORRIED ABOUT?

The 2005 Question: 

What do you believe is true even though you cannot prove it?  

...resulted in book above...the query generated 120 contributions from leading figures in multiple fields of (mostly) science and it caught my attention the year it was posed 
And I believe (and can prove) that I  posted something last year about it as well. 
 The complete archive of answers can be found at: 

http://www.edge.org/responses/what-do-you-believe-is-true-even-though-you-cannot-prove-it 

I recommend checking it out. It's food for thought, served in generous portions. 

And though I'm just an untrained lay person, I'm also, as every blogger knows, under constant pressure to post -so for better or worse here's a few swipes at that which...

I believe, but cannot prove...

No matter where you choose to sit, the tallest person in the theater will eventually be seated in front of you. 

All meetings specifically promoted and organized to establish consensus, will end in contention and acrimony.

The severity and complexity of a malady is always in inverse proportion to the length of time spent in the physician/hospital waiting room.

One bag of microwave popcorn will always be just a little too much for one person and not quite enough for two. 

You"ve seen one, you've seen em all...
Blue Agave field. Jalisco, Mexico. 

There is a single giant underground vat set deep beneath the mountains of Jalisco Mexico, where all the Tequila in the world is created in one batch and siphoned off into a network of tubes leading to all the different "Branded" bottling plants. 

There is no such thing as decaffeinated Coffee 

The next hot thing in telecommunication will be "alibi" apps ...that will automatically send various credible looking malfunction or "error" messages to whomever one wishes to ignore or avoid. 

No one actually knows how Marshmallows are made. 

 Everything in every Hollywood movie is created with computer generated graphics-- including the actors. All actual humans are chosen merely for their resemblances to the CGI characters and are required only to appear on talk shows and provide photo-ops for paparazzi.
The only two things in the universe that can significantly decelerate the passage of time are; travel at (or approaching) the speed of light and the end of an NFL Football game. 

and...NOT A BELIEF, BUT A FACT 
(provided by the highly esteemed and formerly introduced Dr. Mauskop)
The greatest number of surgeries are performed where the greatest number of surgeons live.