In the Philosophy of Religion, one of the four traditional arguments for God's existence.
There are many versions of the Teleological Argument, but they all rest on an analogy between the universe and human artifacts. That is, when we see the teleological organization of the things in the universe (i.e., means adapted to ends) we can legitimately infer a rational mind must have been responsible for the order. As William Paley put it, if we find a watch upon the ground, we would rightly infer there exists a watchmaker. The universe, in its intricate design, is very much like a watch, only much more complex; therefore there must exist a universe maker.
While the Teleological Argument is one of the most popular of all the arguments for God's existence, it does not hold up well under philosophical scrutiny. David Hume has given one of the best responses to this argument in showing that as an argument by analogy the conclusion is only as strong as the similarities between the analogates. Unfortunately, the universe is not really very much like any object of rational contrivance that we know of. But even if it were the case that the analogy between the universe and a machine held, the consequences would be unacceptable for the theist as God would not only turn out to be a contingent being, but also significantly limited in power and knowledge. Hume goes on to argue that if the universe is really analogous to anything in human experience, it would be more like a plant than anything else.