The fine-tuning argument is an attempt to show that the universe is designed. The basic idea of the argument is simple: the parameters of physics and the initial conditions of the universe are such that if some of them, such as the cosmological constant and the gravitational constant, were slightly different, the universe would not have existed. There might still be a universe, but a short-lived or unstable one that does not allow life chemistry, and hence no life --- the universe is intentionally fine-tuned for life.
Let us assume that the physics used in the argument is all correct. Let us even assume that there is no other explanation of the apparent fine-tuning of the universe than that the fine-tuning is actual and intentional. That is, let us assume that the universe does have a fine-tuner or designer.* Call the designer D. What attributes should we ascribe to D? It is clear that D has to be extremely intelligent and powerful (designing a whole universe is no small task!), but do we have reason to believe that D is omniscient and omnipotent?
Although D does not have to be omniscient to design the universe, D may be omniscient. We have no reason to think one way or the other as far as the fine-tuning argument is concerned. However, if D is intelligent enough to avoid doing things that are unnecessary, we do have reason to believe that D is not omnipotent. Consider the following argument:
(1) D fine-tunes the universe for life.
(2) If D is omnipotent, D does not need to fine-tune the universe for life.
(3) D is intelligent enough to avoid doing unnecessary things.
(4) Therefore, if D fine-tunes the universe for life, D needs to do it that way. [from (3)]
(5) Therefore, D needs to fine-tune the universe for life. [from (1) and (4)]
(6) Therefore, D is not omnipotent. [from (2) and (5)]
Anyone who accepts (1) and (3) has to accept the conclusion that D is not omnipotent if she also accepts (2). People who employ the fine-tuning argument certainly accept (1), and it is safe to assume that they accept (3) as well. Do they accept (2)? They have to accept it if they accept all of the following claims:
- If D is omnipotent, D is capable of creating life that is not carbon-based.
- If D is omnipotent, D is capable of creating life of some form in a universe that is utterly different from ours (with different parameters of physics and initial conditions).
- If D is omnipotent, D is capable of creating life of some form even in a short-lived and unstable universe.
They have no reason not to accept these claims because none of the consequents of the conditionals describes an ability to do something that is logically or metaphysically impossible.** So they have no reason not to accept (2).
If God is omnipotent, then D is not God. This is presumably disappointing news for those who employ the fine-tuning argument.
* The fine-tuning argument does not give us any reason to think that there can only be one designer, but for my purposes here it's not necessary to consider the possibility that there is more than one designer.
** Some philosophers argue that 'omnipotence' is an incoherent concept. Here I assume for the sake of argument that the concept is coherent and that the only things an omnipotent being is incapable of doing are those that are logically or metaphysically impossible.