“The author of the ‘Vestiges of Creation’ would, I presume, say that, after a certain unknown number of generations, some bird had given birth to a woodpecker, and some plant to the misseltoe, and that these had been produced perfect as we now see them; but this assumption seems to me to be no explanation, for it leaves the case of the coadaptations of organic beings to each other and to their physical conditions of life, untouched and unexplained.”
This quote is from the Introduction of the first edition of Darwin’s Origin of Species. Now, admittedly, this is out of context, but only slightly so. The point that Darwin makes is sufficiently well-formed that it addresses notions of Intelligent Design and, in the same sentence, dismisses them. Technically, Darwin’s dismissal applies specifically just to the notions around coadaptations, since that is the context within which he is arguing at that point in his introduction.
The dismissal is, in my mind, the perfect scientific argument, because it comes from the central notion of science – namely, a means within which one can explain and predict the nature of the universe. Whenever a scientific theory is put forth, it’s mandatory that the theory make testable predictions. It appears Darwin assumes that the reader will make the logical deduction that an assumption/explanation that leaves coadaptations unexplained is unsatisfactory from a scientific viewpoint.
It’s my understanding that a central tenet of ID is that there is a guiding hand causing adaptation and selection to proceed along certain paths. This is exactly what Darwin is speaking to with “…after a certain unknown number of generations,…”
Now, the amazing thing is that Darwin never says that this tenet, a central part of ID, is wrong, nor that his notions are right. In fact, properly performed science always has the built in humility that a theory that explains all the facts is known a priori to not be provably true, so any good scientist would know that *every* scientific theory is prone to errors. Darwin’s simple requirement, unstated and assumed, that scientific discourse is the context of import leads to the inevitable conclusion by us, the readers, that ID just doesn’t work as a scientific explanation.