The teleological argument for the existence for God is the claim that the world must created and that therefore a creator. There appears to be a purpose to many things; as if we are supplied with nutrition and given abilities and features that allow us to suit our needs. That there are systems in nature that are just too useful or good to be coincidental. If there is a watch — then there must be a watch-maker. 

William Paley was a supporter of the argument by design, using the example of the eye and its usefulness and intricacy, as evidence for God. While seemingly convincing, the argument from analogy fallacy, which (in this case) ignores other body parts that may not be as useful, tries to assume that similarities to some things make it similar to others. 

There’s a number of thinkers since Paley’s time who have pointed out the issues with the argument by design, such as David Hume, and it’s generally considered to be one of the weakest arguments for the existence of God.