The Atheist’s Modal Dilemma.

The Atheist’s Modal Dilemma: When an atheist claims that a state of affairs (e.g., a world where free creatures always choose the good) is logically possible and actualisable by an omnipotent, omniscient, omnibenevolent God, they use possible world semantics identical to the Modal Ontological Argument (MOA). They face a dilemma:

1. The sceptic assumes a coherent concept of God AKA. Maximally Great Being MGB (omnipotent, omniscient, omnibenevolent) when critiquing God’s existence or actions (e.g., claiming God could actualize a world where free creatures always choose the good).

The claim there is a possible world where 'X1' or 'X2' where 'X1' is free creatures always chose the good, and 'X2' is where a MGB exists, are both symmetrical in logic.

2. If the MGB’s attributes are logically coherent, then it is possible an MGB exists in some possible world.

If the properties contain no explicit or hidden contradictions, like a square circle, it is a possible state of affairs.

3. If an MGB exists in some possible world, it exists in all possible worlds (via the MOA, as maximal greatness entails necessary existence).

Note, that if it possible, it exists in at least some possible worlds.

4. If an MGB exists in all possible worlds, it exists in the actual world.

If a MGB exists in some possible worlds,  it wouldn't be maximally great if it didn’t exist in all possible worlds,  including the actual world.  NOTE: necessary existence isn't 'encoded' (as Oppy suggests) rather, if the sceptic can show it is incoherent, the notion never gets past the possibility premise.

5. If the MGB’s attributes are incoherent (i.e., contain a logical contradiction), then critiques assuming those attributes (e.g., Problem of Evil) are invalid, as they target a logically impossible being (a strawman).

C. The sceptic must either (1st Horn) accept the possibility of an MGB, entailing its necessary existence and undermining atheism, or (2nd Horn) demonstrate a logical contradiction in the MGB’s attributes, which invalidates their own critiques and commits them to attacking a strawman.

• Horn 1: Consistency with the MOA:

• If the atheist’s claim (e.g., a specific world is possible) is valid, then the MOA’s premise (an MGB is possible) uses the same logic: if 'X' is logically possible, it exists in some possible world.

• An MGB, by definition, exists in all possible worlds if possible in one, and thus in the actual world (per S5 modal logic).

• Accepting their own logic commits the atheist to the MGB’s existence, undermining atheism.

• Horn 2: Rejecting the MOA:

• To reject the MOA’s premise (an MGB is possible), the atheist must show that the MGB’s attributes (omnipotence, omniscience, omnibenevolence) are logically contradictory, or provide a non-arbitrary reason why their proposed state of affairs is possible while an MGB is not.

• No clear contradiction exists in the MGB’s attributes, and rejecting the MOA’s logic while accepting their own is special pleading unless justified.

• Conclusion: The atheist cannot consistently use possible world semantics to critique God (e.g., “God could actualise 'X'”) while rejecting the MOA, unless they prove the MGB’s attributes are contradictory or provide a principled distinction between their logic and the MOA’s. Without this, their position is either inconsistent or concedes the MGB’s existence.

Challenge: The atheist must either accept the MOA’s conclusion (an MGB exists) or demonstrate why their use of possible world semantics is valid while the MOA’s is fallacious, without relying on arbitrary rejection of the MOA’s conclusion.

Possible objections:

• X1 is merely contingently possible:- the symmetry isn't the same, as X2 implies necessary existence.

If the sceptic claims their claim is only contingently true, God isn’t necessarily obligated to bring it about, meaning this weakens their claim that God should do X1, as there is no obligation to bring it about? God as an MGB is necessary,  but that is only because that would be what an omnipotent and omniscient being would like, omnipotence can't have any contingency in his main properties. However, the claim X2 is possible, could be false, if a contradiction is found, meaning both X1 and X2 are symmetrical in logical structure.

Additionally, even if we grant the contingently possible nature of X1 breaks the dilemma,  it undermines the strength of their critique, as noted before, God isn’t obligated to bring about contingent state of affairs,  moreover this breaks any logical contradiction suggested in the critique in the first place. As God could have reasons for not bringing it about if it is merely contingent.

However, this doesn't break the dilemma, if they use the definition of a MGB to critique the idea of God, it must be coherent enough to begin with, if it isn’t, their critique risks being a strawman and at best, their argument would be redundant as they could have saved time and just shown the contradiction in the first place, to undermine the whole theistic case.

• The Reverse Modal Ontological Argument (RMOA)

The sceptic could try to use the RMOA, which reverses the Modal Ontological Argument by stating a maximally great being isn't possible,  thus isn’t possible in any world. However, this is logically equivalent to saying a MGB is logically impossible, the very claim in question. Additionally, mere symmetry alone isn't enough to establish the RMOA is a possible state of affairs. For instance, the MOA gives a definition of what such a being would be like, namely omnipotence, omniscience and omnibenevolence, these are coherent properties,  with no clear contradictions. The RMOA would need to show why these are incoherent to be a possible state of affairs.

Additionally,  if the sceptic insists the RMOA symmetry means neither the MOA or RMOA is preferred, thus the argument proves and disproves God simultaneously, presenting a contradiction. It seems it equally applies to X1, that is, we can say it isn't possible God can create free creatures that always choose the good (or whatever claim the sceptic makes) and the challenge equally disappears. 

Thus, the sceptic needs to show why X1 is a possible world and X2 isn't without ad hoc assumptions, or be forced to accept X2 is equally true as X1.

Conclusion.

The atheist, must inextricably face their burden of:

1. Accept X2 is possible, undermining their conclusion that God cannot exist. 
2. Why their possibility premise is valid while dismissing the theistic possibility premise of the MOA is invalid, If they cannot show why their claim is valid and the theists is not, they must concede they are being inconsistent in logic. 
3. Shoulder the burden of proof that the concept of a MGB is incoherent, thus undermining their case, as they are using an incoherent notion of God.
4. Retreat to a lesser claim e.g an evidential argument from evil.

• Option 1, is obviously untenable for any self respecting atheist worth their salt. 
• Option 2, shouldn't be accepted lightly, as the burden is high to show why X1 is valid and X2 isn't and if they can't show why, one should try to be consistent in logic, so this seems the most costly to me. 
• Option 3, is probably the most difficult option intellectually, as a clear logical contradiction must be presented, thus triggering the strawman accusation. 
• Option 4, is the only viable option and has the least cost. But this does mean the logical problem of evil is in fact dead.

What do you choose?