Classical Logic
The fundamental laws of thought—identity, non-contradiction, excluded middle—are the foundation of all rational inquiry and point to a rational ground of reality.
Validity, Soundness, and Truth
Logic distinguishes between valid arguments (correct form) and sound arguments (valid with true premises). This distinction is crucial for evaluating arguments for and against theism.
Many classical arguments for God's existence—the cosmological, teleological, and moral arguments—are deductively valid. The question is whether their premises are true. Logic provides the framework; evidence and reason evaluate the premises.
- Deductive Validity: If the premises are true, the conclusion must be true—the form guarantees it. Valid arguments preserve truth from premises to conclusion.
- Soundness: A sound argument is valid with actually true premises—it proves its conclusion. The Kalam cosmological argument, if sound, proves God exists.
- Formal Systems: Logic can be formalized into precise symbolic systems with rigorous rules. This precision enables careful analysis of complex arguments.
- Logical Consequence: Some truths follow necessarily from others. If God is the greatest conceivable being, certain attributes follow necessarily. Logic traces these connections.
The Grounding of Logic
The existence and nature of logical laws raises profound questions. What grounds logical laws? They're not physical—you can't trip over the law of non-contradiction. They're abstract and necessary.
Theism provides a natural grounding: logical laws reflect the rational nature of God. Just as mathematical objects exist as divine ideas, logical laws express the structure of divine thought. The Logos—the rational principle—orders all things.
- The Grounding Problem: What grounds logical laws? They're not physical, not conventional, not contingent. Naturalism struggles to explain their existence and our knowledge of them.
- Divine Intellect: Theism grounds logic in God's rational nature—logic reflects divine thought. The laws of logic are the way God thinks, and creation reflects that rationality.
- Argument from Reason: C.S. Lewis argued: if naturalism is true, our reasoning faculties are products of blind evolution aimed at survival, not truth. This undermines confidence in reasoning—including the reasoning that led to naturalism.
- Self-Refutation: Any attempt to deny logic uses logic. The skeptic who says 'logic is unreliable' relies on logic to make the claim. Logic is inescapable—it is the structure of thought itself.