Underlying nearly every design argument, you’ll find the assumption of ignorance of something and then the conclusion that since we don’t know, then a god must be the proper explanation. Ignored is the question of whether or not an unknown and possibly unknowable god, using unknown and possibly unknowable methods, for unknown and possibly unknowable reasons, can ever be considered a rational “explanation” for anything.
Technically, an explanation is composed of two parts: the explanandum and the explanans. The explanandum is the event or phenomenon or thing which is supposed to be explained. The explanans is the series of statements which is supposed to do the actual explaining. A good explanation is something which provides new information in the explandum which does not appear in the explans. A good explanation is something from which we can learn.
This is not the case when someone says “God created the universe” or “God created human beings” because such statements don’t provide us with much in the way of new and useful information. No “God did it” assertion can “explain” anything at all unless it is accompanied by details about what this god is and how exactly this god and this god’s actions lead specifically to the event that we are trying to explain.
Otherwise, all that has happened is that our ignorance has been slightly reworded from ignorance about the event in question to ignorance about this god — except that we are now ignorant about many things (what is this god, how does this god act, why does this god act, etc.) whereas before we were ignorant merely about the cause of the event. Trading one bit of ignorance for several bits of ignorance and without learning anything useful in the process hardly seems to be a fair trade.
This is true whether the argument is being offered in specific or general terms. Sometimes the argument from design is specific (the eye it too perfect to have arisen naturally, therefore God created it) and sometimes it is general (the universe is too perfect to have arisen naturally, therefore God created it). In both cases, the phrase "too perfect to have arisen naturally" is merely a mask for saying "I can't think of any means by which it could have arisen naturally."
You can tell that this is so by the fact that no arguments are offered for the claim that these things could not have developed naturally. If you ask for one, the response will be something along the lines of "well, you prove that it was possible - and if you can't, that will prove that I'm right." And there you have it: in the absence of any proof that it can happen, the ignorance of how such an event might occur is used to justify the idea that God is behind it all. It's an argument from ignorance, nothing more and nothing less.
