Oprah asks "Waht do you know for sure?"

What Do You Know for Sure?
In her first O, The Oprah Magazine column, Oprah wrote: "We are all the causes of our own effects, …That's why I'll never stop asking the question, 'What do you know for sure?'" Here, notable men and women share the truths that inspire them, guide them, and repeatedly set them free...
19 simple, surprising, brilliant rules to live by
Oprah's all-time top 20 discoveries