The argument from design

I was reading through Richard Dawkins's The God Delusion the other day when I came to the section in chapter 3 about the teleological argument. Dawkins mentions that Darwin's introduction of the theory of evolution defeated that argument, but the argument is invalid anyways, even if we don't know anything about evolution (something which Dawkins does not mention here).

The argument from design, as explained by Dawkins is his book is

Things in the world, especially living things, look as though they have been designed. Nothing that we know looks designed unless it is designed. Therefore there must have been a designer, and we call him God.

This is a subtle case of circular reasoning. The statement "Nothing that we know looks designed unless it is designed" is equivalent to "All things we know of that look designed are designed". However, strictly speaking, unless we've already presumed the existence of a deity, we don't know if living things are designed. We can say they look designed (and that is arguably false), but we have no evidence that they actually are designed. This argument sets out to prove that living things are designed (and therefore god exists), but subtly assumes it.

Of course, evolution does do a very good job of showing that things that look designed can exist without a designer, but that only strengthens the case against this argument, it isn't required to disprove it.