A Razor's Edge

Our planet orbits in what is called the Goldilocks Zone. It's called that because scientists have weird senses of humor. The idea is that the planet is not too hot and not too cold, but just right. The determining factor is whether the planet can have liquid water. From what we know, that is the primary requirement for life. No liquid water, no life.

Our planet also happens to have one moon to help stabilize its orbit, normalizing the climate to some degree. We have an asteroid belt that serves to shield us from many incoming, potentially damagings Rock Of Death From Outer Space.

There are a number of other factors that make our planet particularly suited to life. Some theists see this and say, "It can't be a coincidence that we just happen to show up on the one planet that has all this. We are balanced perfectly on the edge of a razor."

Well, no, not exactly.

This argument supposes that we were somehow destined for Earth, that life couldn't have appeared on another planet if it was equally suited. The argument seems to say that, were Mars equally suited to the genesis of life, it still would not have appeared there.

The entire suggestion puts the cart before the horse. It's like arguing that the shape of the Colorado River is proof of the existence of God, because it happens to fit perfectly into the Grand Canyon. If either the Grand Canyon or the Colorado River had a different shape, there would be constant flooding all through Northern Arizona. It shows a fundamental misunderstanding of the mechanics behind the operation of water.

Life, with evolution and natural selection, is very much like water. It seeks a niche and continues to work at that niche until it dries up. If it doesn't dry up, it creates the Grand Canyon.

It's not a coincidence that the Colorado River happens to fit perfectly into the Grand Canyon, but nor is it proof of design. That's just how it works.

Also bear in mind that our planet has only been able to support life some of the time. It also isn't a coincidence that we happened to show up in that time. Nor is it proof of design.