Sean McDowell wrote a blog post that has a very simple illustration to show what the fine-tuning argument is about, and then he supplies one of the best known illustrations: the strong force.

Here’s the simple illustration:

I grew up in the mountain town of Julian, California. I have always enjoyed walking the mountain trails and hiking in the woods. I have introduced my young children to exploring the forests.

Let’s assume I’m out hiking with my son Scottie. About two hours into our hike Scottie says, “Dad, I’m getting tired. And I’m thirsty.” Right then we catch sight of what looks like a structure through the trees. As we approach, we see a picture-perfect cabin in the middle of the woods. The door has been left wide open.

Scottie and I make our way into the cabin. To our amazement my favorite music is playing. Scottie’s favorite Wii video game appears on the TV screen. We see a sign on the refrigerator that says, Favorite Drinks Inside. Scottie runs over, opens the refrigerator, and takes out a Sierra Mist. “Can you believe this, Dad?” he blurts out just before guzzling down his drink. This would all be just too amazing, right?

What would you conclude by all this? Could these circumstances have come about by sheer chance? It would seem that someone had to have known we were coming and designed the cabin, the music, game, and drinks with us in mind.

While this fantastic cabin discovery is just a story, the reality is that Planet Earth is even more amazing and fantastic. As with the cabin illustration, it is as if someone carefully prepared our world exactly with us in mind. Certain laws of nature rest within very narrowly defined parameters that allow humans to exist here.

You can click through for the strong force point, which is one of the oldest and best-recognized instances of cosmic fine-tuning. The thing to note is that fine-tuning doesn’t just mean fine-tuning for humans. It means that unless these constants and quantities are set exactly right, then there will be no life of any kind.

The strong force example he introduces has to be fine-tuned in order to have chemical diversity – elements that include hydrogen, but also other elements other than hydrogen. You cannot make any kind of life out of only hydrogen. And you cannot make life without hydrogen. Any kind of life needs water. And water has to be made with hydrogen. So, in order to have life, you need some hydrogen, but you have to have more than just hydrogen because you need other elements, too. The production of hydrogen depends on the fine-tuning of the strong  force.