In other words -- how do you embrace the questions while still providing answers? Designers have a a fairly accurate stigma surrounding them. People who work with designers often have the same complaint: "designers always think they're right." Sometimes, they are right -- but in the event that almost infinite solutions could be found for the same problem (which I believe is always the case), their inability to form a new opinion can be crippling.
That said, the opposite -- designing with uncertainty -- is also not advisable. As Bob Johansen, of Palo Alto's Institute for the Future, observes, "weak opinions are problematic because people aren’t inspired to develop the best arguments possible for them, or to put forth the energy required to test them."
In Bob Sutton's words, the solution is to have 'Strong Opinions, Weakly Held," going on to say that you should "fight like you're right, listen like you're wrong."
Andy Grove put it another way when he said he wanted all his people to have "strong beliefs, loosely held."
And John Lilly carried the concept into a design-specific bit of advise when he made the case that a designer should "design like you're right, read the data like you're wrong."
Ultimately they're all conveying the same important idea: that a designer (or any problem solver) should be driven by strong, well-formed opinions that they're willing to defend -- and ready to upturn at any moment.
Bob Sutton approaches this concept from the angle of someone trying to define the difference between intelligence and wisdom. In his book, Hard Facts, he makes the observation that the wise are "those who have the courage to act on their knowledge, but the humility to doubt what they know."
I think many people jump between the two -- from great confidence in their knowledge and ability to great doubt in their conviction and acceptance of the unknown. It's the ability to operate as both people at once -- the authoritative opinion, and the humble student -- that proves mastery.
And that may be a process of recreation. One of my favorite quotes is by Henry Sidwick:
"One has to kill a few of one’s natural selves to let the rest grow—a very painful slaughter of innocents."
As Andy Grove put it, you need to "act on your temporary conviction as if it was a real conviction; and when you realize that you are wrong, correct course very quickly."
At the end of the day, moving forward can be accomplished only one way: by moving forward. Tom Petty has the best advice of all: "Don't dither; you can always change your mind later." In his words, I aspire to be "confident... but not really sure."