The organ of spiritual knowledge is obedience. Just as you open your eyes to see colors, you know the presence of the kingdom of God by obeying. You act on the knowledge you have. And in acting you encounter the reality of the kingdom. This is not some esoteric knowledge but claims that can be tested publicly. These knowledge claims are verifiable. As you obey, you yourself will be tested — at times severely. In those times, hold fast to the idea that you do have knowledge. As you do, you will come to know the goodness and rightness of the teachings of the Christian faith. — Dallas Willard

Renewing the Christian Mind: Essays, Interviews, and Talks