Q: We can detect bad design in biology when…
1.) something is not designed the way we would design it.
2.) we discover a flaw in the design.
3.) we can conceive a better design.
4.) the design is contrary to known design principles.
5.) we can't, without independent knowledge of the designer.
Answer and discussion below the fold.
A: 5.) we can't, without independent knowledge of the designer.
Let's look at a couple of hypothetical situations that illustrate why this is so.
Scenario 1: Purpose.
A group of cavemen discover a paper airplane and a 1:30 scale plastic model of a WWII P-51 Mustang. Our noble ancestors immediately make an inference by analogy in that the two objects share many characteristics with other flying objects: birds. They hurl the Mustang off a cliff and watch disappointedly as it crashes to the valley floor. They then throw the paper airplane and excitedly jump up and down as it soars over the horizon. "Mustang, bad design", mutters one fellow to himself, unable to realize he incorrectly judged the purpose.
Scenario 2: Intent.
Our troop of troglodytes then come upon a space shuttle. This time, they correctly guess that it was designed for the purpose of flight. They turn the key and grunt excitedly as the control panel lights up. Then they push the vehicle off the cliff and watch it crash to the valley floor. "Shuttle, bad design" they laugh, unable to see that they misjudged the designers intent.
Irrational Design is not Bad Design.
Our cavemen approached the problem by trying to guess purpose and intent, then comparing the objects to their guess. All answers are equally right or wrong in this scenario. A model P-51 Mustang is good design or bad design depending upon our guess at it's purpose or intent.
So how do we avoid conflating irrational design with bad design?
The way we avoid this is by first looking at rational and irrational features of the design, and THEN attempt to glean purpose and intent from those rational and irrational features. Not the other way around.
But shouldn't we look at irrational designs as flaws? What if we can conceive of a better way to design something? Can't we rightly call something bad design if we find something obviously wrong with it? Our cavemen might have had similar ideas: Maybe by shaving several tons off of the space shuttle it could be made more like the well-designed, rationally designed paper airplane?
Compromised design is not a sign of bad design. Why? Because design is ALWAYS a compromise. There will never be an aircraft with optimal stability and optimal maneuverability. There will never be an aircraft with optimal weight and optimal strength. There is always a compromise between a variety of design principles based upon – you guessed it – purpose and intent. One could always look at the space shuttle and conclude that it's lack of maneuverablility is a design flaw. But purpose and intent reveal to us that a compromise was made for very rational reasons.
And more importantly, we can understand that since there is always compromise in design, there will always be an element of irrationality in design.
It may be tempting, upon examining the vertebrate eye for example, to infer that wiring the optic nerve to the front of the retina was an irrational design, and therefore a bad design. But as we have seen, without knowledge of the purpose or intent we cannot make any determination about whether this design is good or bad.
The correct approach is to find a rational feature of design (a nerve connection to the retina), and begin building a scenario of purpose and intent from there.
Good? Bad? Who knows?
Rational? Irrational? In design we expect to find both.
Intelligent design? Investigate, use critical thinking, and decide for yourself if the rational and irrational features we find lend themselves to a scenario of purpose and intent.