Well, clearly the
primary purpose of the eye is to see. The eye may have also some secondary purposes we’re not aware of, however, a design which fails at its primary purpose is a failed design, as simple as that.
Human eye, the favorite example of creationists is so badly designed, that I don’t know where to start:
- It takes six muscles to move the eye, while three would suffice. No, these muscles are not redundant. Any engineer knows that more elements = more failure points, which is why designs should be kept simple.
- Focusing is done by deforming the lens, while the same goal can be achieved by moving the lens with respect to the detector (retina). The result is that in humans, focusing becomes more difficult with age, because the lens becomes more rigid, while muscles become weaker. In contrast, the moving lens design is not only simpler, but does not have the aging problem. A 100-year-old telescope will still focus perfectly.
- Retina… oh boy, failure upon failure. First of all, connections from the light-sensitive cells are routed on the light-facing side, reducing light collecting area, while it would be more logical to route them on the back side, and use the space saved for more sensory surface (better night vision!). Second, all connections are routed to one point where they cross to the other side and run to the brain – this creates a blind spot. On top of that, the optical nerve not only connect eye to the brain – it also serves as a pipe used to regulate liquid pressure within the eye! In other words, you have these fragile nerve fibers used as pipe which must carry pressure.
There are other problems, but I’ll stop here.
The human eye is clearly a bad design, which fails at its primary purpose. This means that the designer was incompetent.
Creationists counter that by saying that the designer must have had some other considerations which caused compromises in the design. Well, what might these be? The eye serves no other major purpose besides seeing. So we must conclude that humans have been
intentionally given badly designed eyes. However, that would mean that the designer wanted to make their life more difficult than necessary – i.e., the designer was evil.
To make matters more interesting, there are creatures which have eyes which are designed correctly – these are the cephalopods. Which would mean that the designer was obviously capable of designing a better eye, but for some reason, equipped humans with failed eye. Again, this suggest intentionally sabotaging the design in order to make user’s life more difficult – i.e. evil.