The most decisive criticism of the very idea behind “Intelligent Design” theory (ID) is that it is a “Science Stopper”. There is no such thing as evidence either for or against ID, because “God did it” is not an explanation. It is simply away of filling a gap in our knowledge with an empty rhetorical flourish. If there is a God, he created everything in the Universe, and thus to use this claim as an explanation for a particular occurrence is either trivially false or trivially true.
There are, however, two other science stoppers which are not acknowledged as such.
1) The concept of “direct awareness”, so beloved by positivists and other empiricists. To say something is directly given implies we have no explanation for how we are aware of it. I believe Hume refused to define experience, because its meaning was allegedly obvious. Ned Block made a similar claim for “phenomenal consciousness”. In this context, the word “obvious” basically means “any prejudice that is so widely accepted that no one feels a need to justify it.” The prejudice here is that because we are all familiar with experience, it does not require an explanation. However, once scientific explanations became available for how our experience arises, the idea of direct awareness was rejected. The essential point here is that this would have happened regardless of what explanation was discovered. Once there a mechanical cause-and-effect explanation for our experience, it would by definition no longer be direct. In much the same way, “God created Life” seemed plausible until Darwin showed us how Life was created. However, the God-referring explanation would have been rendered inadequate by any possible causal explanation. Because of the principle of sufficient reason, explanations like “we are directly aware of X” or “God created X” are both science stoppers waiting to be filled by causal explanations. Chalmers apparently rejects the principle of sufficient reason as a metaphysical truth, for he believes that “there is nothing metaphysically impossible about unexplained physical events”. If so, what criteria does he suggest we use for dismissing Intelligent Design?
2) The concept of “Intrinsic Causal Powers.” This concept stops us a little further down the road, but stops us nevertheless. Causal explanations always need to see certain properties as intrinsic, so they can map and describe the relations between those intrinsic properties. If causal explanations didn’t stop somewhere and start talking about the relationships between something and something else, they’d never get off the ground. But this pragmatic fact about scientific practice does not justify the metaphysical claim that there are certain causal powers which are “intrinsically intrinsic.” Paradoxically, intrinsicality is itself a relational property. A property which is intrinsic in one science (say chemistry or biology) must be analyzable into a set of relationships in some other science (for example, physics). To deny this is to limit us to descriptions, and stop us from finding explanations.
One brand of physicalism claims that only very tiny particles possess intrinsic powers, but this contradicts another “physicalist” claim that brains have intrinsic powers. Those who believe in the mind/brain identity theory claim that environmental factors may cause experiences, but brain states embody those experiences. This is a fancy way of saying that brains have the intrinsic causal power to produce mental states, just as knives are intrinsically sharp. But saying that knives are sharp is just short hand for saying that they can participate in bread-cutting events, cloth-cutting events etc. Talk of sharpness intrinsically inhering in knives, or mental states inhering in brains, is accurate enough for many purposes, but it mires us in an Aristotelian world of dispositional objects which limits scientific progress.