Monday, November 15, 2010

God and the Necessity of Logic

Is logic dependent on God? Some have gone so far as to say that God is logic, simply as a matter of identity. Others, such as Plantinga, hold that logic, insofar as it can be expressed propositionally, constitute one of the "divine ideas," or thoughts of God. One argument against this goes something like this:

1. Logic is necessary. (Premise)

2. Whatever is necessary cannot be contingent. (Definition)

3. If logic is dependent on God, then logic is contingent. (Definition).

4. Therefore, logic is not dependent on God. (From 1 - 3)

The problem with this argument, and we find a similar problem with the Euthyphro Dilemma, is that it unambiguously equivocates the term, "contingent." In (2), "contingent" refers to contingency-as-possible-non-instantiation, whereas in (3), "contingency" refers to contingency-as-dependency. Only the former of the two definitions necessarily entails the non-necessity of logic.

To show that this is the case, suppose that A exists necessarily. Now imagine that A necessarily entails B. B is therefore necessary as well, but it is also dependent on A. Therefore, B is both necessary and dependent.

For this reason, it is probably best to use the term, "dependent," when referring to contingency-as-dependency. "Contingency" may then be reserved only for possible non-instantations. This may help alleviate the common confusion.


  1. Good point Doug on pointing out the equivocal fallacy there. But how do you think this applies to the Euthyphro dilemma? In the usual formulation the term "good" seems to be used in the same sense throughout.

    P.S. On an unrelated note, where did you find this argument in Scotus?

  2. Or wait. Do you mean that in the Euthyphro Dilemma, they use a syllogism similar to the above, and make the same equivocal fallacy when it comes to "dependence"?

    Also, just wondering, what do you think of theistic activism? I think it sort of relates to this business here.

  3. Hey man, good to see you posting here. I discovered Scotus' argument while reading Rowe's book, "The Cosmological Argument." Even though Rowe takes a mostly critical view of cosmological arguments, I think he's well worth reading.

    With respect to the Euthyphro Dilemma, I often hear the charge that if moral values are dependent on God, then God can change them on a whim, which would imply contingency. I've just never found that reasoning plausible.

    Theistic activism is interesting, but there are several problems with it. The biggest difficulty, in my view, is the fact that abstract objects are causally inert, so it's hard to understand how they could be created by God in any way. I think a good alternative to theistic activism is theistic conceptual realism. You may wish to take a look at Greg Welty's paper on the subject:

  4. Walter Van den AckerNovember 17, 2010 at 6:01 AM

    Good points here, Doug
    I totally agree with your criticism of the argument (hey, we actually agree on something for a change).
    That logic is dependent on God does not mean, however, that God has any power over logic.
    Your definition of dependence also entails that God is dependent on logic, BTW.

  5. You're right to say that it doesn't imply that God has power over logic. In fact, I'm not sure what that would mean, given that power is something restricted to causally efficacious entities. Whether God is dependent on logic is an interesting question, but God's self-existence simply means that He is not dependent on any causally efficacious entity that exists independently of Him.

  6. Hi Doug, in regards to what walter said,

    If A is necessary and B is "dependent" on A because A entails B, then A will also be "dependent" upon B in the same sense. That is, if A is necessary, then

    B entails A

    is true, since A cannot but be true. Given material conditionals, if the consequent is necessarily true, then anything entails it.