Wright’s argument: Suppose you’re a Martian and you’re given a fertilized cell. You have never seen anything like it. You have no idea how it came to be (simply by chance or designed either by a natural selection process or by a conscious designer). You look at it and you see it grow and develop into a duck. Would you conclude, on the basis of this single data point, that it is a designed thing (rather than something that appeared by chance)? If yes, isn’t the entire Earth eco-system just like that? It started from something very simple and gradually evolved into something very complex. I.e. shouldn’t we take more seriously the idea that perhaps the entire process of evolution has a meta-purpose (such as building complexity and intelligence)?
Yudkowsky’s argument: No, the analogy is weak because internal elements in the eco-system have cross-purposes, e.g. a fox chases a rabbit, rather than cooperating for a single meta-purpose etc. while all the organs in the duck observed by the Martians work for a single purpose.
Wright argues that 1) the Martians, on the basis of seeing just that single duck, don’t really have very strong evidence supporting the idea that the duck has an optimized design, 2) similar correlations can be seen within the eco-system (e.g. plants produce oxygen for animals etc.), and 3) one cannot easily dismiss the idea that the observed cross-purposes (such as the fox/rabbit example) don’t have a higher optimization role.
The discussion: link
The old discussion with Dennett on the same subject referenced by Wright: link