Taner’s post on the argument that the “laws of logic” require a transcendent ground (i.e., God) understandably dismissed that argument. It is silly. However, it is the kind of silliness that has just enough of a plausible ring to it to give it rhetorical impetus. So, to prevent it from doing mischief, it is good to point out its fallacies. Here is the quote Taner gave from creationist Jason Lisle:

Laws of logic are God’s standard for thinking. Since God is an unchanging, sovereign, immaterial Being, the laws of logic are abstract, universal, invariant entities. In other words, they are not made of matter—they apply everywhere and at all times. Laws of logic are contingent upon God’s unchanging nature. And they are necessary for logical reasoning. Thus, rational reasoning would be impossible without the biblical God. The materialistic atheist can’t have laws of logic. He believes that everything that exists is material—part of the physical world. But laws of logic are not physical. You can’t stub your toe on a law of logic.

There are so many things wrong with this one short passage that it is hard to know where to begin. Let’s skip the host of philosophical questions we could put to Dr. Lisle about what he considers THE laws of logic to be, and glide over the numerous arcane debates over deviant logics, etc. Let’s consider modus ponens. Can a materialistic atheist consistently invoke modus ponens? Now, as Dr. Lisle implies, modus ponens is not a physical thing. But it is not a non-physical thing either. It is not an entity of any sort. It is a rule that can be expressed in the form of a hypothetical imperative: “If you have ‘if p, then q,’ and you have ‘p,’ then conclude q.” There is nothing at all mysterious, transcendent, or otherworldly about such a rule. It is just an instruction, an effective procedure for getting a valid inference from the given premises. A materialistic atheist in no way violates his ontological commitments by following modus ponens or affirming it as a valid rule of inference. Such an atheist would be guilty of inconsistency only if he followed Dr. Lisle in illicitly reifying the rules of inference, turning them into transcendent entities. But he doesn’t.
Well, what about the law of noncontradiction? That is a law of logic if anything is. Is it somehow inconsistent or otherwise inappropriate for a materialistic atheist to invoke the law of noncontradiction? The law of noncontradiction states that for any proposition p, ~(p & ~p), that is, it is not the case that both p and not-p. Do we need a transcendent ground or supernatural basis to justify or validate this rule? No, all we need is to recognize the futility of rejecting it. If someone wishes to reject that law, then he is giving us permission to insert “it is not the case that” in front of any sentence he utters. Philosopher Robert Fogelin tells an amusing story about an occasion when he found himself debating the law of noncontradiction with a number of postmodernists and post-structuralists. These “advanced thinkers” reviled the law of noncontradiction as an excrescence of “logophallocentric” Western rationalism. Fogelin asked if any of them were applying for funding from the National Endowment for the Humanities. Several indicated that they were. Fogelin then asked them whether it would make any difference to them if the answer to their request was no rather than yes. Unsurprisingly, this query provoked an eruption of rage. Fogelin had neatly shown that anyone who rejects the law of noncontradiction cannot assert anything at all, not even whether they would rather have a grant than not. Such a “negative” demonstration of the law of noncontradiction is all that we need. God is superfluous. The law of noncontradiction is not an abstract, ideal entity. It is simply a rule we have to follow if we are to communicate anything at all.
Lisle says some other very strange things, like “Laws of logic are contingent upon God’s unchanging nature.” This implies that if, per impossible, God’s nature were to change, the laws of logic would change too. But how could the laws of logic be contingent upon anything, even God’s nature? Is Lisle saying that there are possible worlds, maybe ones created by changeable, illogical gods, where modus ponens would not be valid? How could this be? Even odder is his claim that rational reasoning would be impossible without the biblical God. Couldn’t Allah be the eternal ground of logic? Why not Platonic ideas? Why not the Flying Spaghetti Monster?
Again, I sympathize with Taner’s back-of-the-hand treatment of this argument. It is hard to take seriously such a fatuous farrago of non-sequiturs. Maybe Taner’s instincts are better here, because a number of writers have found out, by bitter experience, that rational responses to “arguments” like Lisle’s often evoke extended and truculent replies by “presuppers.” Responding back will get you into an endless loop of argument, since presuppers, like creationists, are masters of argumentum ad exhaustum, argument by saying the same thing over and over again until your opponent quits from exhaustion. Still, though, I think that as long as silly arguments get an audience, someone needs to point out the silliness.

About Keith Parsons
  • http://www.blogger.com/profile/11983601793874190779 Steven Carr

    ‘It is a rule that can be expressed in the form of a hypothetical imperative: “If you have ‘if p, then q,’ and you have ‘p,’ then conclude q.”’

    I suppose you have read Lewis Carroll’s dialogue between Achilles and the Tortoise where the subject of justification of this rule was discussed at some inordinate (nay, infinite) length.

  • http://www.blogger.com/profile/18201878060264233090 B H

    Its this theistic argument that makes me wish high school and general college math courses taught the basics of formal systems and model theory in addition to statement logic and calculus. The whole argument seems to be ignorant of how/why mathematics developed in the first place and what a formal model actually is.

    I’m left wondering if the guy in the sky who invented the law of noncontradiction is the same dude who thinks 0.999… is equal to 1? the same one who thinks we can have a set of all sets that are not members of themselves? Or maybe he only invented natural numbers and second order typed logic and the above foibles of math/logic are errors of human approximation?

  • http://www.blogger.com/profile/12763971505497961430 Jeffrey Shallit

    People who argue that the “laws of logic” are “eternal and unchanging” clearly haven’t heard of things like multiple-valued logics or probabilistic logic.

    My colleague Tim Kenyon in Philosophy says that there aren’t really “laws of thought”; it is more like the “municipal regulations of thought”.

  • http://www.blogger.com/profile/16826768452963498005 Jim Lippard

    Quine: “Change of logic, change of subject.” (Looks like this blog is a good place to get into the philosophy of logic…)

  • http://www.blogger.com/profile/00763792476799485687 J. J. Ramsey

    “I’m left wondering if the guy in the sky who invented the law of noncontradiction is the same dude who thinks 0.999… is equal to 1?”

    Errm, 0.9999… is equal to 1.

  • http://www.blogger.com/profile/18201878060264233090 B H

    Yes. That’s why I mentioned it…

  • http://www.blogger.com/profile/02653303041185240250 Andrew

    If the laws of logic are not inherent in the nature of the universe, but merely human constructs, that presents one problem for the atheists…the subjectivity of logic.

    If, however, the laws of logis are inherent in the nature of the universe, independent of human construct…that is an entirely different problem.

  • http://www.blogger.com/profile/15467379458813206767 Johan
  • Jonathon von Tischner

    You didn’t research the whole argument did you? Atheists use laws of logic because they come from a logical God who made everything, He doesn’t claim you have to be a believer to use them. Also, he deals with other ‘gods’ and how they don’t meet the preconditions of intelligibility. You still haven’t refuted the arguement, you’ve actually strengthened it by being logical at all lol.