Uncertainty Refutes Plantinga’s Modal Argument

Uncertainty Refutes Plantinga’s Modal Argument 16/12/09

Following the lead of Agrippa's Trilemma, Vagon utilizes a practical application of its consequences with relation to Plantinga's Modal Ontological Argument.

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Having established a lack of epistemic certainty, we can leverage Plantinga’s own modal ontological argument for his god and turn it against him, showing his argument is incoherent at best and damning at worst.

Alvin Plantinga’s modal ontological argument is designed to provide a logical proof for the existence of a god with certain characteristics. It uses axiom S5 which says if possibly necessarily P, then necessarily P, to show that a god for which we can think of no greater being exists necessarily in all words:

  1. By definition a maximally great being is one that exists necessarily and necessarily is omniscient, omnipotent and perfectly good. (Premise)
  2. Possibly a maximally great being exists. (Premise)
  3. Therefore, possibly it is necessarily true that an omniscient, omnipotent and perfectly good being exists (By 1 and 2)
  4. Therefore, it is necessarily true that an omniscient, omnipotent and perfectly good being exists. (By 3 and S5)
  5. Therefore, an omniscient, omnipotent and perfectly good being exists. (By 4 and since necessarily true propositions are true.)

To even need such an argument is to question the possibility of such a being itself, but while this is worthy of consideration it is not sufficient to refute premise 2.  For example we may test the possibility of a human walking without removing the ability of a human to walk. Instead we need to question the justification of the possibility of a maximally great being.

To do this we now turn back to the lack of absolute certainty established from Agrippa’s Trilemma . A lack of certainty is literally saying we cannot be 100% sure of any particular proposal. We know from probability that any outcome less than 100 is possible, despite however remote. This leads us to an interesting conclusion:

  1. By definition Plantinga’s maximally great being is one that exists necessarily and necessarily is omniscient, omnipotent and perfectly good. (Premise)
  2. Possibly a maximally great being does not exist. (Premise)
  3. Therefore a maximally great being does not exist. (By 2 and since necessarily true propositions are true.)

Or in plain language, a maximally great being must exist in all worlds, therefore if it is possible that it does not exist in one world then it can exist in none. Uncertainty makes all things possible, therefore Plantinga’s god does not exist.

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  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    I disagree with this analysis. To say possibly a maximally great being does not exist, still implies that possibly a maximally great being does exist. If Plantinga is allowed to have that premise obtain, then he completes his argument. To say that possibly, it is necessary that a maximally great being does not exist is just to say that it is impossible that a maximally great being exist. I think that premise would require some additional support, presumably by showing an incoherence in the attributes of God.

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    I disagree with this analysis. To say possibly a maximally great being does not exist, still implies that possibly a maximally great being does exist. If Plantinga is allowed to have that premise obtain, then he completes his argument. To say that possibly, it is necessary that a maximally great being does not exist is just to say that it is impossible that a maximally great being exist. I think that premise would require some additional support, presumably by showing an incoherence in the attributes of God.

  • http://www.wearesmrt.com/bb Vagon

    I think support is the key issue here. Platinga offers no support for the possibility of a maximal being other than saying he (or Anselm or whoever) has defined it that way.

    I’m trying to establish that by looking at his argument with the support of uncertainty leads to the reverse conclusion of his original (and by contrast unsupported) argument.

    A more extensive refutation of his premise I would apply reductio ad absurdum (maximally evil entity), the incoherence of the omnis and this reversal, but I wanted to keep the scope tight.

  • http://www.wearesmrt.com/bb Vagon

    I think support is the key issue here. Platinga offers no support for the possibility of a maximal being other than saying he (or Anselm or whoever) has defined it that way.

    I’m trying to establish that by looking at his argument with the support of uncertainty leads to the reverse conclusion of his original (and by contrast unsupported) argument.

    A more extensive refutation of his premise I would apply reductio ad absurdum (maximally evil entity), the incoherence of the omnis and this reversal, but I wanted to keep the scope tight.

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    Right. I agree that a rebuttal of (2) is required in order to beat Plantinga's argument. But, the only possible rebuttal of (2) is to show that such a being is impossible. I don't agree that uncertainty leads us to this conclusion.

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    Right. I agree that a rebuttal of (2) is required in order to beat Plantinga's argument. But, the only possible rebuttal of (2) is to show that such a being is impossible. I don't agree that uncertainty leads us to this conclusion.

  • http://www.wearesmrt.com/bb Vagon

    Okay well maybe I can rephrase.

    Platinga has suggested that a maximally great being exists in all worlds, however uncertainty shows that we cannot make this absolute statement. Therefore Platinga is suggesting an incoherent onotology.

  • http://www.wearesmrt.com/bb Vagon

    Okay well maybe I can rephrase.

    Platinga has suggested that a maximally great being exists in all worlds, however uncertainty shows that we cannot make this absolute statement. Therefore Platinga is suggesting an incoherent onotology.

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    Well, technically he's suggested that a maximally great being exists in merely one world, and he has deduced that it therefore exists in all. If we are to combat that premise, that a maximally great being possibly exists, we must somehow show that a maximally great being is impossible. Even with uncertainty, how can we deny that premise without asserting an equally as strong one ourselves?

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    Well, technically he's suggested that a maximally great being exists in merely one world, and he has deduced that it therefore exists in all. If we are to combat that premise, that a maximally great being possibly exists, we must somehow show that a maximally great being is impossible. Even with uncertainty, how can we deny that premise without asserting an equally as strong one ourselves?

  • http://www.wearesmrt.com/bb Vagon

    Well the claim of uncertainty (for better or worse) is an equally strong assertion, but lets suppose uncertainty in and of itself is insufficient to refute the argument.

    Instead lets propose a maximally evil being: Dog. That is Dog is also necessarily omniscient, omnipotent but instead perfectly evil. Along the same lines we deduce Dog exists. It is not possible for these beings to exist in the same world without compromising there abilities to be perfectly evil/good.
    So:
    1. A maximally good being exists (Platinga)
    2. A maximally evil being exists (Dog)
    3. Neither can exist in the same world without compromising there maximal excellence.
    4. We cant be sure whether either exists.
    5. Therefore neither exists.

  • http://www.wearesmrt.com/bb Vagon

    Well the claim of uncertainty (for better or worse) is an equally strong assertion, but lets suppose uncertainty in and of itself is insufficient to refute the argument.

    Instead lets propose a maximally evil being: Dog. That is Dog is also necessarily omniscient, omnipotent but instead perfectly evil. Along the same lines we deduce Dog exists. It is not possible for these beings to exist in the same world without compromising there abilities to be perfectly evil/good.
    So:
    1. A maximally good being exists (Platinga)
    2. A maximally evil being exists (Dog)
    3. Neither can exist in the same world without compromising there maximal excellence.
    4. We cant be sure whether either exists.
    5. Therefore neither exists.

  • http://www.wearesmrt.com/bb Vagon

    Forgive the typos…

  • http://www.wearesmrt.com/bb Vagon

    Forgive the typos…

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    I see where you're going, but I don't accept that both cannot exist in the same world. On the moral factor, there is no inherent contradiction between a perfectly good and perfectly evil being existing, lest they be able to destroy each other. But why should we assume that one omnipotent being can destroy another? If omnipotence is the power to do all that is possible (loose definition), and the destruction of an omnipotent being is impossible, then it seems that both beings must co-exist.

    Also, your move from (4) to (5) does not seem warranted. Practically, if (4) holds we may act as if (5) is true, but it does not seem to follow.

  • http://intensedebate.com/people/MitchLeBlanc MitchLeBlanc

    I see where you're going, but I don't accept that both cannot exist in the same world. On the moral factor, there is no inherent contradiction between a perfectly good and perfectly evil being existing, lest they be able to destroy each other. But why should we assume that one omnipotent being can destroy another? If omnipotence is the power to do all that is possible (loose definition), and the destruction of an omnipotent being is impossible, then it seems that both beings must co-exist.

    Also, your move from (4) to (5) does not seem warranted. Practically, if (4) holds we may act as if (5) is true, but it does not seem to follow.

  • http://www.wearesmrt.com/bb Vagon

    I disagree. The whole argument rests on the impossibility of a maximumly great being having these limitations. Consider Anselm and his “I can imagine no greater being” from which it is derived.

    If you limit this being, who is then to say the maximum this great being can be is in 99.99% of all worlds?

    Uncertainty (whether it be the possibility of non-existence or a question of the attributes) ruins any of these absolutes.

  • http://www.wearesmrt.com/bb Vagon

    I disagree. The whole argument rests on the impossibility of a maximumly great being having these limitations. Consider Anselm and his “I can imagine no greater being” from which it is derived.

    If you limit this being, who is then to say the maximum this great being can be is in 99.99% of all worlds?

    Uncertainty (whether it be the possibility of non-existence or a question of the attributes) ruins any of these absolutes.

  • http://www.wearesmrt.com/bb Vagon

    The move from 4-5 was intended to be taken in context with the impossibility of a necessary being to not exist in some world from the original post. Sorry should have included that, a bit sloppy on my behalf.

  • http://www.wearesmrt.com/bb Vagon

    The move from 4-5 was intended to be taken in context with the impossibility of a necessary being to not exist in some world from the original post. Sorry should have included that, a bit sloppy on my behalf.

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