#872 Abandoning Logic to Avoid God

Dr. craig’s response

James, your friend’s proposed escape route for avoiding the argument’s conclusion is not only desperate but in the end actually represents the final triumph of the argument itself.

In order to see this, let’s first clear up your friend’s confusion about the nature of logic. The laws of logic, including the basic rules of logical inference, do not apply to or govern concrete things but apply to propositions.[1] We consider the logical form of a sentence in abstraction from its content and on the basis of these logical rules infer one proposition from another.

For example, one well-known rule of inference is called modus ponens, which states that if some proposition p is true, then if p implies another proposition q, then q is also true. Notice that it doesn’t matter what p and q are about; we consider only their logical form. Modus ponens holds for any propositions whatsoever.

You yourself used this logical rule of inference in your above argument. It is modus ponens (along with some other logical principles) that validates the inference from “Everything that begins to exist has a cause” and “The universe began to exist” to “Therefore, the universe has a cause.” Your friend agreed with the validity of this argument. So he accepts modus ponens. On what grounds, therefore, is he sceptical about modus ponens when reasoning about the cause of the universe, since logical rules of inference are independent of factual content?

It is inept to ask whether “this 'cause' is subject to the laws of logic.” To repeat, propositions, not concrete things, are subject to the laws of logic. Moreover, these propositions may be about anything:  things that begin to exist, the universe, the cause of the universe – it doesn’t matter. All that matters is the logical form of the proposition along with the rules of inference governing deductions of one proposition from another.

Logic, like mathematics, is a purely a priori discipline that does not depend upon concrete conditions. So if I offer the argument 

The cause of the universe is either an abstract object or a personal mind.

The cause of the universe not an abstract object.

Therefore, it is a personal mind.

you may dispute the truth of my premises, but the validity of the inference is guaranteed by the rule called disjunctive syllogism: p or q; not-p; therefore, q. It’s no good to say that the cause of the universe is not subject to the rule of disjunctive syllogism. For the logical rule applies to any propositions, regardless of their content.

Now we see the desperation of your friend’s escape route. He has to deny logic itself. He has to deny the rules of inference such as modus ponens, modus tollens, hypothetical syllogism, conjunction, disjunctive syllogism, and so forth. But these logical rules of inference seem to be necessarily true. It is metaphysically impossible that if p implies q, and p is true, then q is not also true. Just think about it. Your friend should be sobered by the realization that these rules of inference are universally recognized as necessary truths. That strongly suggests some lack of understanding on his part.

Moreover, such a denial of the rules of logic is self-defeating and unlivable. When your friend draws an inference like “Possibly, the cause of the universe is not subject to the laws of logic; therefore, possibly, arguments about its attributes are invalid,” he is using the logical rules of inference to make that deduction! In fact, he is actually using the resources of modal logic, the logic of possibility and necessity, to justify his inference. So his argument defeats itself. And never mind his argument; anyone who denies the necessity of the rules of logic will be utterly unable to get along in life. He could not safely infer, for example, “If it’s Sunday, the library will be closed; today is Sunday; therefore, the library is closed.” That makes his position unlivable.

Again, it’s no use trying to deny the laws of logic only with respect to the cause of the universe, for the rules of logic are not about concrete things, but about propositions and apply to the logical form of these propositions, without regard to their content.

I said above that your friend’s escape route is not only desperate but actually represents the final triumph of the theist’s argument. For think of what your friend is saying! In order to deny the conclusions of the arguments about the attributes of the first cause, one has to deny logic. Do you realize what that means? If he is right, then atheism is illogical. You have to abandon logic in order to maintain atheism. Atheism is therefore irrational. It is not religious believers who are illogical and irrational, but unbelievers.

The goal of a theistic argument is to raise the intellectual price tag of unbelief as high as possible. No higher price can be exacted for scepticism than abandoning the rules of logical inference. In other words, far from representing an escape route from the argument, your friend’s gambit is the ultimate victory of the argument. To avoid its conclusion, the sceptic has to deny logic itself.