What Is Paley's Watch Analogy?

The 'watch analogy' from William Paley is an 'a posteriori' (based upon experience, as opposed to the use of logic) argument for the existence of God. The argument makes use of an anaology as Paley compares a watch and the Earth/universe. The argument hinges upon the assumed premise that 'like causes resemble like effects'. Paley argues that if we were to come across an object, such as a watch on a beach, we would not assume that it had got there by chance since we would notice how complex it is and that its individual parts work together within the mechanisms of the watch. Paley likens this to the complexity of the world and argues that the world exhibits similar, if not suprior complexity. Therefore, we can infer, since like causes resemble like effects, and both the watch and the world show signs of complex and intelligent mechanisms, both have been designed by an 'intelligent designger'; the watch by humans and the world by God. Therefore, by this argument, Paley concludes that an intelligent God exists and this God created the world.