Some proponents of Intelligent Design claim that it is not inherently theistic. Here I argue that Intelligent Design probably reduces to theism given defenses of cosmological arguments, and that any attempts to avoid a reduction to theism do not work; and thus I.D. is not on identical methodological footing with naturalistic evolution. I further argue that a proponent of both nontheistic Intelligent Design and most cosmological arguments must drop one of these things to avoid epistemic tension. I do not argue here that either Intelligent Design or naturalistic evolution is likely true or false, that one methodology should be preferred to the other, or that we should be neutral with respect to methodology*.
Consider the following thesis of Intelligent Design:
ID1: The cause of the first life (self-replicating organism) on Earth is best explained by Intelligent Design.
If true, this conception of I.D. implies that the first life was caused by some sort of intelligence not originating on Earth. This alone is not necessarily theistic, but if I.D. best explains life on Earth, what best explains life not on Earth? Maybe it’s some form of intelligence (aliens, A.I.) that arose naturally elsewhere in the universe. But then we must ask, what best explains that?
The reasoning behind I.D. is that life is best explained by intelligence because of information content in the genome, specified complexity, or something similar. This hypothetical otherworldly life would almost certainly also exhibit these traits. So I.D. must explain that as well.
This move can be made for every natural form of life in the universe: earth life to alien life 1, alien life 1 to alien life 2, etc. But once these jumps are exhausted, and all natural life is accounted for via a natural intelligent agent(s), the only place left to go is to the supernatural.
This again does not necessarily imply theism; there are several possible moves here. One is an appeal to abstract objects as a cause of an intelligent agent. But this has implications for the cosmological argument. William Lane Craig, in responding to some objections to his Kalam cosmological argument, argues that abstract objects are distinguished from concrete objects by their inability to stand in causal relations. If this response to objections is dropped, then it is a trivial matter to object to the KCA by positing an abstract object as the cause of the universe. If it is not dropped, then an appeal to an abstract object as the cause of the first life in the universe cannot be made.
Another possible move to “save” I.D. from theism is to posit a contingent supernatural intelligence (i.e. an angel, a ghost, etc.) But this has implications for liebnizian and thomistic cosmological arguments, which require causal principles that state every contingent thing or instance of coming into existence must have a cause. If this principle is accepted, these arguments conclude that there must be a god. To drop this for the sake of non-theistic I.D. means that such arguments don’t go through.
A further concern for positing either abstract objects or a contingent supernatural intelligence is that they are ad hoc – they are being posited solely to “save” nontheistic I.D., and have no other basis. This has implications for Robin Collins’ fine tuning argument. His argument relies on a restricted version of the Likelihood Principle (“an observation e counts as evidence in favor of hypothesis h1 over h2 if the observation is more probable under h1 than h2”), which adds that LP can only be applied to cases where a hypothesis is not ad hoc.
In conclusion, nontheistic Intelligent Design has no viable options for explaining the first life in the universe which to not also undercut various cosmological or fine tuning arguments for God; thus there is epistemic tension between positing both a nontheistic Intelligent Design and such arguments; and perhaps even between nontheistic Intelligent Design and theism due to the case for theism being greatly weakened by nontheistic I.D.
*These debates are, I believe, separate issues.
 William Lane Craig, “The Kalam Cosmological Argument”. The Blackwell Companion to Natural Theology. pg. 193
 Alexander Pruss, “The Liebnizian Cosmological Argument”. The Blackwell Companion to Natural Theology. pg. 25
Robin Collins, “The Teleological Argument”. The Blackwell Companion to Natural Theology. pp. 205-206