From the dawn of history, science has probed the universe of unknowns, searching for the uniting laws of nature.
Donald Rumsfeld
There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.
Gever Tulley
Tinkering is a way of understanding difficult problems, of wrapping our heads around them and quantifying the unknowns.