Extrapolation and the Design Inference
The design inference in a nutshell:
Every time we observe X (be that CSI or IC) and know the cause it has always been via agency involvement. Always. Meaning there has never been an observed instance of X (be that CSI or IC) arising spontaneously, ie without agency invlovement. Never.
Therefor when we observe X (be that CSI or IC) and don't know the cause we can infer, due to our knowledge of cause and effect relationships in accordance with uniformitarianism, that an agency was involved.
True the usual evotardgasm is "Man (humans) are the only agency we know of that produces X (be that CSI or IC)", but that is the point of extrapolation.
Ya see if we have already determined design and we also have determined that man (humans) could not be the agency, then we infer it was some other agency-> extrapolation.
So simple my eight year old understands it...