To reiterate, ID is not an alternative mechanism as the intelligent designer is the user of the mechanism and not the mechanism itself.
eh? I don't understand. You want someone to explain how a hypothetical designer designed different forms of life? If and ID is given, why is that not sufficient to explain diversity?
I think it's in a similar vein as saying that 'descent with modification' is insufficient to explain diversity. In order to explain the diversity of species on this planet, one needs to explain the process of
natural selection - the mechanism of natural selective pressures (resource availability, predation, atmospheric conditions, yadda yadda yadda, bisque) affecting populations and the manner in which such pressures affect fecundity to arrive at subsequent speciation (traits that do not impede reproduction having a greater tendency to be passed down).
Ataraxia, is that kinda what you're going for? Would the following satisfy:
The mechanism behind ID is
divine modification. At some point between conception and birth, a
divine entity, through some as-yet undiscovered physical means,
directly modifies the genes of the pre-born entities for some as-yet undiscovered goal. This is not a process of
natural selection, as things like 'survivability' do not make a significant contribution to determining if a gene or trait is passed down.
Selection for continued reproduction is result of a
divine willful entity interacting with the physical world on to-be-born organisms.
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As an aside, I have yet to see any real definitions or descriptions behind what 'intelligent' means in reference to ID. So far as I can tell, there is nothing that bars the process of natural selection as a viable candidate for the 'intelligence'.