I was at a prayer meeting recently and when we were praying for specific requests, someone asked God to reveal His will beyond a shadow of a doubt. We prayed for this person, but not until someone spoke up:
“For faith to exist, there must be a degree of uncertainty.”
Adam,
A great missionary to China (Hudson Taylor) said something similar. I think his wording is a little superior to the phrase you quoted, but both are saying the same thing.
“Unless there is an element of risk in our exploits for God, there is no need for faith.”
–Hudson Taylor
http://en.wikiquote.org/wiki/James_Hudson_Taylor