One of the major arguments made by the intelligent design crowd is that people can recognise design. They argue that if it looks designed, then the default argument should be that it is designed. This leads to arguments that run something like “you [scientists] need to provide a complete, step by step account of how this evolved, otherwise Darwinism is a failed theory”. Obviously that’s nonsense…it amounts to saying that if the exact pathway is unknown, then we should reject it in favour of a totally unspecified mechanism.
Even taken from an in-universe perspective, ID hinges on the assertion that we can recognise design. There’s a very insightful post at Ooblog which looks into the question of recognising artefacts, and asks why it is that the IDists aren’t pursuing this field of research. Their entire “theory” hinges on the assertion that we can recognise artefacts. If they had any sort of a scientific agenda, they should be investigating something that’s so fundamental to their “theory”.