Humans are surrounded by mystery and are themselves deeply mysterious. One of the profoundest mysteries in human experience has to do with our relation to time. Time is so much a part of our lives that we take it for granted. Our bodies even measure it with heartbeats and circadian rhythms. Yet when asked what time is, we do not know how to answer.

One of the greatest thinkers in western history, St. Augustine of Hippo, mused: “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.”

Philosophers have long debated the nature, and even the existence, of time. The brilliant Cambridge philosopher and mathematician Bertrand Russell believed that our experience of the flow of time is an illusion. For Russell, time does not flow, it simply is.

His colleague at Cambridge, the philosopher J.M.E. McTaggart, went even further. He argued that Lord Russell was mistaken: It is not the flow of time that is illusory; time itself is an illusion. McTaggart rejected the concept of time altogether.

The Christian philosopher William Lane Craig has defended a more traditional view of time. If I understand him correctly, he argues that there is an objective and transcendental time - a God-time - by which human (and any other) time is measured. But the Australian philosopher J.J.C. Smart claims this entails an infinite regress: If we measure our time by God’s time, then we must measure God’s time by a time that transcends it, and on ad infinitum.

Physicists are of little help on this score. Paul Davies, Regents’ Professor at Arizona State University, calls time “dynamical” and says it can be “stretched by motion or gravitation.” Even time, Einstein discovered, obeys the laws of physics. But this only tells us what time does, not what time is. Is it a medium through which we move, like a boat through a river? Or is it something that moves around us, like a river around an island, as in Isaac Watts famous line, “Time, like an ever-rolling stream, bears all its sons away”? Is time an illusion? Is our experience of it an illusion?

We are back with Augustine: “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.”

Humans are able to look back on the past but are unable to enter it. They are unable to look into the future yet they must enter it. This may provide us with a clue to understanding the purpose of time, even though we are incapable of understanding its nature. God made humans temporal creatures so that they would have the opportunity to trust him.

If our relationship to time were different, if we were capable of moving around in time the way we now move around in space - forward and backward, in and out - the future would not be a mystery to us. We would know what is going to happen tomorrow and the next day, next year and far into the future. But there is good reason to think that under such circumstances faith would be impossible.

If I promise you $20 and you believe the promise, the surest way to put an end to that belief is to give you the $20. As soon as you have it in hand, faith is unnecessary; indeed, it is impossible. Faith requires an unseen future to exist. And the existence of faith is essential to our wholeness as human persons.

According to the Bible, faith is needed if a conversion to a spiritual life is to begin. Faith is also needed for that spiritual life to continue. As St. Paul says, “we live by faith.” Faith is also necessary to the fulfillment of the spiritual life. It plays an essential role, St. James taught, in the completion of human beings. In other words, life with God begins with faith, proceeds with faith, and reaches its desired end with faith.

There is time - quite literally: Time exists rather than some non-temporal reality - so that humans can exercise faith. The universe is, at bottom, relational and not merely material, and enduring relationships are based on faith.

Shayne Looper is the pastor of Lockwood Community Church in Branch County, Michigan. Read more at shaynelooper.com.