A Vital Understanding of Christianity – A Modern Day Rendering of ‘Mere Christianity’

What do Christians really believe—and why does it matter?

In A Vital Understanding of Christianity, David O. Harrison offers a clear, compelling exploration of the foundational truths of the Christian faith. With warmth, insight, and clarity, he leads readers through the heart of the gospel—from the reality of moral law and the problem of sin to the hope found in Christ’s death, resurrection, and return. Drawing on Scripture, reason, the inspiration of C.S. Lewis, and life experience, Harrison addresses the deepest questions of the human heart while stripping away religious confusion and cultural clichés. Whether you’re curious about Christianity, a new believer, or seeking to deepen your faith, this book invites you to rediscover the breathtaking simplicity and eternal significance of the good news. Accessible yet profound, this is Christianity explained for real life—anchored in truth, full of hope, and overflowing with grace.

The Cover Image

Creating the cover image became an unexpectedly emotional experience.

Not long ago, I was reading Luke 23 when I came to the account of the penitent thief. He and I have more in common than you might suppose. Perhaps you do too?

There comes a moment when the light breaks through—when you realize that Jesus is exactly who He claimed to be. Your whole attitude towards God changes. The One you dismissed, doubted, or resisted becomes the One you desperately need.

For the thief, that moment came as he hung in excruciating pain on a cross, crude iron nails through his hands and feet. For me, it came as I sat on the floor, facing bankruptcy, shouting at the top of my voice, “God, if you’re there, help me!”

Different circumstances. The same desperate turning towards God.

Then I read these words:

“Jesus, remember me when you come into your kingdom.”

Jesus answered him, “Truly I tell you, today you will be with me…”

Luke 23:42–43

You will be with me.

I lingered over those words.

I have been hugged by God—more than once. I have heard His voice, been overcome and broken by His majesty, and been blessed, encouraged, and disciplined by Him many times. I am grateful for every encounter, and I yearn for more.

But what I long for most is to be with Him. Forever.

The Christian band MercyMe recorded one of the most moving songs I have ever heard: I Can Only Imagine. It invites us to consider what it might be like to stand in the presence of Jesus. Reading Luke’s account, I found myself imagining what the thief saw, heard, felt, and did later that very day.

Jesus completed His promise with the words “in paradise.” What a glorious promise. Yet, for those of us who know Him, the greatest wonder is surely in the words that come before it: “with me.”

To be with Him would be enough. Paradise is the overflowing generosity of the God who gives us more than we could ever ask or imagine.

And that is how I picture myself on the front cover: held closely and lovingly by the One who forgave me, died for me, and rose again so that I could be with Him forever.

I invite you to imagine yourself in this picture.