There are three fundamental laws of logic. Suppose P is any indicative sentence, say, “It is raining.”
The law of identity: P is P. The law of noncontradiction: P is not non-P. The law of the excluded middle: Either P or non-P.
The law of identity says that if a statement such as “It is raining” is true, then the statement is true. More generally, it says that the statement P is the same thing as itself and its different from everything else. Applied to all realty, the law of identity says that everything is itself and not something else.
The law of non-contradiction says that a statement such as “It is raining” cannot be both true and false in the same sense. Of course it could be raining in Missouri and not raining in Arizona, but the principle says that it cannot be raining and not raining at the same time in the same place.
The law of the excluded middle says that a statement such as “It is raining” is either true or false. There is no other alternative.
The laws of logic are:
Immaterial
Transcendent
Unchanging
Universally applicable.
To deny them is to use them therefore no person can rationally deny the existence of the laws of logic.
The laws of logic flow from the biblical worldview. The very nature of God—unchanging, universal, and immaterial — is the source of the laws of logic. Being made in His image, we have the capacity to use these laws of logic to reason correctly and identify fallacious reasoning. On the other hand, naturalism does not provide any basis for the laws of logic, so the existence of these laws demolishes naturalism.
Some conjecture that the laws of logic are just human conventions we agree upon. But such conventions would not be universal, and different people or cultures could choose different standards of logic. Debate would be futile.
Perhaps the naturalist might conclude pragmatically that humans follow the laws of logic because they work. This explanation skirts the issue. Where do these laws come from? How could immaterial laws of logic come from a strictly material universe? As Dr. Jason Lisle asked, “if the brain is simply the result of mindless evolutionary processes that conveyed some sort of survival value in the past, why should we trust its conclusions?”
If the laws of logic are not laws governing correct reasoning but just descriptions of the way the brain thinks, then no one could ever be guilty of being irrational or breaking a law of logic.
Furthermore, if the laws of logic actually existed materially in the brain, they would not be universally true, and people could have different laws of logic depending on their particular brain connections.