A Presuppositional Defense of Theism

“The fear of the Lord is the beginning of knowledge; fools despise wisdom and instruction.” – Proverbs 1:7 (ESV)

The existence of God is not a hypothesis to be tested by autonomous human reasoning, but the necessary precondition for reason itself. Presuppositional apologetics, most notably championed by Cornelius Van Til and Greg Bahnsen, asserts that all knowledge, logic, and morality depend upon the triune God revealed in Scripture. Unlike evidentialist approaches that appeal to so-called neutral reason, presuppositionalism demonstrates that neutrality is a myth—everyone operates from a worldview, and without the Christian worldview, rationality itself collapses. The question is not whether one believes in God, but whether one can make sense of anything without Him.

This approach is not merely an alternative apologetic strategy—it is the only one that fully upholds the authority of God’s revelation. It demonstrates that the denial of God is not merely false, but epistemologically self-refuting. The unbeliever, in rejecting God, unwittingly borrows from the Christian worldview to make arguments against it. Without God, the unbeliever cannot account for truth, logic, or morality.

The Impossibility of the Contrary

Van Til famously asserted that denying God results in epistemological futility. Human knowledge, logic, and ethics require an absolute, immaterial standard—something that only makes sense if the God of Scripture exists. Greg Bahnsen demonstrated this masterfully in his debate with atheist Gordon Stein, where he asked:

“In your worldview, what justifies the laws of logic?”

Stein had no answer. The presuppositional challenge is this: If God does not exist, what accounts for the universal, immaterial, invariant laws of logic? The atheist assumes logic exists, but his materialistic worldview cannot justify it. Bahnsen pressed the issue:

1. If logic is merely a product of the human brain, then different brains could produce different logics, leading to absurdity.
2. If logic is a social construct, then different societies could invent contradictory logics, undermining the very possibility of rational discourse.
3. If logic is merely a function of nature, then it should be subject to change, but logic is unchanging.

Only the Christian worldview provides a sufficient basis for the laws of logic, which reflect the thinking of the eternal, rational God (John 1:1). Without God, all reasoning becomes arbitrary.

Philosopher Alvin Plantinga, while not strictly presuppositionalist, strengthens this argument with his evolutionary argument against naturalism. He states:

“If naturalism and evolution are true, then our cognitive faculties are the result of blind evolutionary processes aimed at survival, not truth. But if that is the case, we have no reason to trust our cognitive faculties—including the belief in naturalism itself.”¹

Thus, atheism is self-defeating. It must assume the reliability of reason while embracing a worldview that destroys any foundation for trusting it.

Atheism Borrows from Theism

Atheists frequently claim objective morality, rationality, and uniformity in nature—yet their worldview provides no justification for these concepts. C.S. Lewis captures this contradiction when he writes:

“If the whole universe has no meaning, we should never have found out that it has no meaning.”²

Moral objectivity is one of the clearest examples of this inconsistency. Atheists denounce actions such as genocide or slavery as objectively wrong. However, on atheism, morality is either a social construct (which makes it subjective) or a byproduct of evolution (which makes it arbitrary). William Lane Craig presents a devastating critique of this moral inconsistency:

“If God does not exist, objective moral values do not exist. But objective moral values do exist; therefore, God exists.”³

Presuppositional apologetics goes further—it shows that even the atheist’s moral outrage is an admission of God’s existence. The unbeliever, in calling something “evil,” presupposes a moral law—but a moral law requires a moral lawgiver. As Van Til put it, “The unbeliever must sit in God’s lap to slap His face.”⁴

A Syllogistic Form of the Argument

This transcendental argument can be formally structured as follows:

1. If God does not exist, then the preconditions of intelligibility (logic, morality, uniformity in nature) do not exist.
2. The preconditions of intelligibility do exist (as evidenced by rational thought, objective morality, and scientific inquiry).
3. Therefore, God exists.

This is not a probabilistic argument—it is an absolute proof. Without God, reasoning itself collapses.

The Self-Attestation of Scripture

Christianity is not merely the most rational worldview—it is the only rational worldview. Scripture is the self-attesting authority that undergirds all knowledge. Van Til argued that attempts to prove God by appealing to “higher” standards elevate human reason above divine revelation. Instead, Christians should recognize Scripture as the ultimate standard.

“All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness.” (2 Timothy 3:16)

John Frame elaborates on this by distinguishing between proof, persuasion, and necessity in apologetics:

“While evidences and arguments are valuable, they must be presented within the context of the Christian worldview, where God’s revelation is the ultimate authority.”⁵

Thus, apologetics is not merely an intellectual exercise—it is a confrontation of worldviews.

The Challenge to Unbelief

The presuppositionalist does not merely argue for God’s existence but challenges the unbeliever’s ability to argue at all. Every attempt to deny God presupposes God. This is why Van Til stated:

“The only proof for the existence of God is that without Him you couldn’t prove anything.”⁶

Atheism is not merely false—it is self-defeating. The atheist must assume the very things his worldview cannot justify. Greg Bahnsen illustrates this with a devastating analogy:

“The atheist is like a child sitting on his father’s lap, slapping him in the face—but he would not even have the ability to slap if his father were not supporting him.”⁷

The unbeliever must either recognize the Christian worldview as the necessary foundation for rationality or embrace absurdity. There is no neutral ground.

The God Who Must Be

God is not merely a conclusion at the end of an argument—He is the starting point of all thought. Christianity does not ask for blind faith but calls us to recognize the self-evident reality of God’s existence. Without Him, reason collapses, morality becomes subjective, and science loses its foundation. The presuppositional stance is clear: Christianity is true because the impossibility of the contrary demands it.

The unbeliever may deny God with their lips, but every act of reasoning, every moral judgment, and every scientific discovery testifies to the God they cannot escape. As Cornelius Van Til declared:

“To argue against God is to argue against the very foundation of argument itself.”⁸

Footnotes

¹ Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (New York: Oxford University Press, 2011).
² C.S. Lewis, Mere Christianity (New York: HarperOne, 2001).
³ William Lane Craig, Reasonable Faith: Christian Truth and Apologetics (Wheaton: Crossway, 2008).
⁴ Cornelius Van Til, The Defense of the Faith (Philadelphia: P&R Publishing, 1955).
⁵ John Frame, Apologetics to the Glory of God (Phillipsburg, NJ: P&R Publishing, 1994).
⁶ Cornelius Van Til, Christian Apologetics (Phillipsburg, NJ: P&R Publishing, 1976).
⁷ Greg Bahnsen, Always Ready: Directions for Defending the Faith (Covington, LA: American Vision, 1996).
⁸ Cornelius Van Til, The Defense of the Faith (Philadelphia: P&R Publishing, 1955).