The Design argument for the existence of God

The Design Argument for the existence of God.

• a teleological argument
• a posteriori argument because it's based on external evidence

The design argument is in two parts:

• Design Qua Regularity (design in relation to order and regularity in the universe)
• Design Qua Purpose (design in relation to the way parts of the universe fit together for a purpose) -developed in the 17th century in response to new scientific discoveries.

Thomas Aquinas

The design argument formed the fifth of Aquinas's five ways, he argues from design qua regularity stating that everything is directed toward an end, even inanimate objects are directed to an end and have some purpose, this purpose must be directed by some external power. He likens this to an archer shooting an arrow at a target, the archer directs the object to reach its end, the arrow is therefore the universe and the archer; God. He concluded that the way in which natural bodies act in a regular fashion to accomplish their end, provides evidence of an intelligent designer, this designer being God.
Although Aquinas talks of design qua regularity, it could be argued that his argument in design qua purpose as he talks about things having an end goal and a purpose for existing.

William Paley(1743-1805)

put forward his design arguments in his book; Natural Theology.

Design qua regularity

just as a formal garden shows evidence of a designer, by the lack of weeds and the order and regularity in the flower arrangements, the universe shows evidence of a designer, by the rotation of the planets and natural laws such as gravity. Philosophers conclude that just as the garden didn't come about by chance, neither did the universe, both were designed.

Paley used evidence from astronomy and Newtons laws of motion and gravity to prove design in the universe. Paley pointed to the rotation of the planets in our solar system, and how they all obey the same universal law, and hold their orbits because of gravity, noting how even slight irregularities in this order would result in chaos, surely this could not have come about by chance. He concluded that some external agent must have imposed order on the universe as a whole, and this agent must be God. 

Design qua purpose

in the 17th century it had been proved that the planets orbited the sun and Newton had discovered gravity, there was a new mechanistic way of viewing the universe.

Paley put forward the most famous form of the design argument; the analogy of the watch, saying that suppose he picked up a rock off the ground and examined it, then questioned where it came from, he would feel quite content if the answer was 'it's been there forever', but suppose he picked up a watch from the ground and examined it, then questioned where it came from, he would not be content with the previous answer, because he would see the sheer complexity and skill behind the watch, how each of the individual pieces fit and…