The Dumb Watchmaker
I have heard it many times. Theists trying to use a watch to prove there's a God. In case you are one of the lucky few who hasn't heard this comparison, here it goes:
"If you find a watch in the desert, you immediately assume there's a watchmaker. Why? Because everything that is designed needs a designer. Therefore, when you see the universe, when you see life, you should assume there's a designer."
There are variations of this argument. The "Look at this banana" argument, and the look at this painting argument that Kirk Cameron used in the ABC "Atheist-theist" debate.
For starters, if I see a watch on the ground, I assume there's a watchmaker, yes. Why I don't assume is that the watchmaker always was. Doing so would be explaining something as complex as a watch with something even more complex: the watchmaker. Theists claim the universe needs a designer, and that the designer always was. This is no different than saying the watchmaker always existed, and one day, he pulled a watch out of his ass. This is just lazy thinking. You cannot explain something complex with something even more complex that requires even more of an explanation.
There is another problem with the watch-watchmaker analogy. The idea that a designer needs to be a "thinking being". Lightning is a very complex phenomenon requiring thousands of volts, and a place to strike. A place that can absorb electrical energy. Does that mean every lightning has a Lightning Engineer in the clouds? No. The laws of nature make it possible for lighthing to exist. Likewise, evolution makes life a possibility.
The designer in these cases is the laws of nature. That being the case, mistakes are made, for the designer is not a thinking being. It is a dumb watchmaker, working through rules, with nothing that can stop him from making mistakes. 90% of the species that inhabited this planet are gone. Most mutations result in failures. More than half of the stars that have existed in the univerve have probably become supernovas. The solar system is full of asteroids that failed to become planets. Only one planet in our solar system supports life. The latter failed in Mars, and it probably failed in the thousands of planets that inhabit the Milky Way galaxy. Some designer we have.
We lack a thinking designer. We have a designer that goes by rules. A dumb watchmaker. Richard Dawkins would say "blind watchmaker", but I think that's a little prejudicial toward blind people, for most of them could learn how make watches even though they can't see.