A number of years ago, I was having dinner with a dear friend who was experiencing a season of significant spiritual darkness. He was struggling with doubt. He hadn’t given up his faith, but he felt the pull. Internally, he was wrestling over what appeared to him like dissonant truth claims. Externally, he was wrestling over the profound brokenness and suffering of the world, some of which had suddenly emerged in his family.

We’re a lot alike, my friend and me. We both take life very seriously and process information, observations, and experiences through a similar inner reality detector, overseen by our skeptical inner inspector. We both have a melancholic streak, and since we’re both amateur musicians, we’re both drawn to songwriters whose compositions reflect and articulate our complicated perceptions of reality.

So, as my friend described his wrestlings, he read me some quotes from a songwriter who had once been a Christian but had since lost his faith. The lyrics were raw, honest descriptions of life in the world as the songwriter now saw it — like Ecclesiastes, but without any hope that God exists and will bring any ultimate justice or redemption. My friend admitted the lyrics were dark, but at the time they seemed to him to describe reality more accurately than the gospel-laced songs we sang together at church.

He knew that, years earlier, I had wrestled with similar questions during a spiritually dark season, so he wanted to know what I thought. The first thing that came to my mind was the title phrase from an older song by Switchfoot: “The Shadow Proves the Sunshine.” Those five words launched us into a fruitful discussion about the nature of spiritual light and darkness.

What Are Light and Darkness?

Imagine you and I are sitting in a booth at a restaurant, and I asked you the following questions. If you can, pause for a moment after each question and try to answer it before reading on.

In the physical world, what is light — that thing emitted by the sun, or a fire, or a light bulb?

If you attempted an answer, my guess is that, even if you found it harder than you expected, you came up with one or more fairly accurate descriptions of what light is.

If you referred at all to darkness in your previous answer, try now to explain what light is without any reference to darkness.

If you made an attempt, my guess is that, perhaps after finding it a little more challenging, your answer likely was essentially the same.

Now, describe to me what darkness is without making any reference at all to light. But you have to say more than “darkness is dark”; you have to describe what darkness is without contrasting it at all with light.

Could you do it? Can you meaningfully define what darkness is with no reference or inference to light at all? If you can, please share your definition with me, because I think it’s impossible. And here’s why.

Why We Have Eyes

Light, as we experience it in the world, is electromagnetic radiation. In other words, light is actually a thing. But darkness is the absence of light. In other words, darkness isn’t a thing, it’s the absence of a thing. Trying to describe darkness without any reference to light is like trying to describe nothing without any reference to things. Nothing is the negation of things (no thing). Without things, the term nothing would be completely meaningless. And I think the same is true of darkness; it’s the negation of light. Without light, the term darkness would be completely meaningless.

The fact that light exists is the reason we have eyes. We wouldn’t have them if we lived in a universe in which light didn’t exist. And though millions of people can survive and thrive in our world even if their ability to see is for some reason disabled, they’re only able to do so with help from others who can see.

What’s true about eyes is true of all our physical perceptional abilities. The reason we, as a species, have them is because the reality we live in requires them.

Now, if we live too much in our heads and philosophically ponder how we know what’s really real, it’s possible to get stuck in a skeptical solipsism and like Descartes doubt just about everything, which leads to some very dark places. Because reality is more complex and multidimensional than our individual reasoning power alone can detect. And here is one way our physical senses can ground us: the very existence of our perceptional abilities bear witness to the nature of physical reality. The reason we have eyes is because light exists.

Why We Have Spiritual Eyes

All of this leads me to that line from the Switchfoot song: “The shadow proves the sunshine.” In addition to physical perceptions, we also have spiritual perceptions. And we have these spiritual perceptions for the same reason we have our physical perceptions: because the reality we live in requires them. We wouldn’t have them if we didn’t need them.

How is it that we even know to call spiritual darkness dark? And when we perceive reality and our own existence to be dark and foreboding, why do we describe it as dark and why does it feel foreboding? Why does it depress us and make us anxious and fearful? I think it’s because, even if our reasoning powers alone can’t make sense of everything, our spiritual perceptions — what Paul calls “the eyes of [our] hearts” (Ephesians 1:18) — tell us that spiritual light exists.

Darkness is not a thing; it’s the absence of a thing. We know what darkness is because we know what light is. Light, on the other hand, is not dependent on darkness to exist. That’s why the apostle John said, “The light shines in the darkness, and the darkness has not overcome it” (John 1:5). Something can obstruct the sun’s light and produce a shadow that makes our surroundings dim, but the obstruction does not extinguish (overcome) the sun.

What the Shadow Proves

As I told my friend that evening, this reality doesn’t answer all the hard questions or address every doubt. As an apologetic, it’s not even specifically Christian. But I do believe it is a pointer to the nature of ultimate reality, and a precious one to those who find themselves walking through darkness.

We have eyes because there is a sun. So why do we have spiritual “eyes” that long for spiritual light? When we’re walking through the valley of shadows, how is it that we discern the shadows? If we say, “Surely the darkness shall cover me, and the light about me be night” (Psalm 139:11), how is it that we can still distinguish day from night?

It is, I believe, because our very experience of spiritual darkness bears witness to the existence of spiritual light. The shadow itself proves the sunshine. And if that’s true, if we seek the sun rather than the shadows and all the questions they raise, what we’ll find is the light of the world, which is the light of life (John 8:12).

This has helped me in my seasons of darkness, and it helped my friend in his. Perhaps it will shed some needed light into your life or the life of someone you love.