By David K. Clark

Logic involves principles that govern how humans should think and speak.  Studying logic means investigating correct reasoning.  Traditionally, logic is said to begin with three basic laws:  identity, noncontradiction, and the excluded middle.  According to the law of identity, if a statement is true, then it’s true.  Noncontradiction says that if a statement is true, then it can’t be false.  The excluded middle asserts that a statement is either true or false.  Logic includes such laws, but there is more to it as well.

People observe various kinds of laws—moral, natural, mathematical, legal, and logical laws. Some laws declare what ought to be.  Moral and legal laws say what a person should do, although it is possible to violate them.  (For instance, people should tell the truth but often don’t.)  Other laws describe what actually is.  Natural laws assert what does happen under certain natural conditions.  Theoretically, natural laws are consistent and reliable (although it’s possible for a stronger opposite force to overcome a weaker force as in a tug-of-war.)

Logic has an ought component.  This makes logic somewhat like math.  If a shopkeeper wants to make a profit and regularly gives $50 in change to customers who pay with $20 bills, she violates logic.  But this isn’t a moral transgression; it’s a logical blunder.  She’s not acting immorally but irrationally.  It’s wise to think logically.

What is the ground or foundation of logic?  Human logic is patterned after reality.  The Creator built logic into the structures of the physical and spiritual worlds.  The principles of logic reflect a deep reasonableness that characterizes both God and God’s creation.  Because the logic of human thought and speech is grounded in God and God’s work, logic is not arbitrary.

People suggest in several ways that logic is arbitrary.  Some say logic isn’t a discovery of the human mind detected in reality but an invention of the human mind imposed on reality.  They claim that logic is arbitrary because it’s grounded in how humans choose to think.

This position yields a problematic consequence: it disconnects human thought from reality.  It implies that human interaction with the real world fundamentally distorts that world.  The human mind recalibrates the input of the real world to fit its own inward configuration.  So there’s no telling whether human thinking has any connection with reality.  That is troubling, for life and action require knowledge of the real world.  (In addition, someone stating this position is likely refuting himself.  He is probably saying that the truth about the real world is that human thinking is imposed on reality.)

Others say that logic is grounded in culture, not in objective reality.  Different cultures have different logics.  For example, people commonly say logic is a Western invention that Asians successfully ignore.  Logic is arbitrary because it’s rooted in random cultural habits.

This is a misunderstanding.  While people of various cultures may think about different content and begin at varied starting points, the deep reasonableness that governs human thinking is the same.  Consider an analogy.  An African tribesman counts lions.  An Eskimo with no knowledge of lions counts seals.  Both count according to mathematical principles.  Similarly, the content of thought obviously differs from place to place, but the underlying reasonableness built into the creation will govern human thought regardless of culture.