A radical shift in the Zeitgeist was occurring: authority began to be questioned; a skeptical relativism spread among the intelligentsia; claims about God and moral absolutes were rejected; human belief was perceived to be nothing more than a social-construction; the Christian worldview continued to crumble, its primacy supplanted by secularism.

The postmodern age may have started late in the second millennium, but it isn’t so different from the post-Renaissance era, circa 1630.

Into that age of skepticism came the French Catholic mathematician and philosopher René Descartes. Attempting to reestablish a firm footing for knowledge, he decided to make a clean sweep of presuppositions by clearing away all that could be doubted. He applied the method with the precision of a mathematical proof. Cutting away anything that could be doubted, Descartes was left with only one piece of data that was clearly indubitable: the fact of his doubting.

Doubting is a form of thinking, and thinking requires a thinker. The existence of the I that was doing the doubting, therefore, could not itself be doubted. Descartes discovered the apparent foundation for all knowledge: Cogito ergo sum—I think, therefore I am.

To modern ears the phrase is a cliché, and Descartes’ choice of ground for thinking seems obvious. But in the mid-seventeenth century it marked a revolutionary philosophical shift away from the classical and Christian mind that had relied on authority and revelation for centuries. As Richard Tarnas explains in The Passion of the Western Mind, “Descartes unintentionally began a theological Copernican revolution, for his mode of reasoning suggested that God’s existence was established by human reason and not vice versa.”

While starting with the best of intentions, the Jesuit-trained Descartes undermined the Christian worldview for centuries because he made the mistake of starting with epistemology rather than ontology, with knowing rather than being. Necessarily, what is is prior to what can be known, for knowing itself implies both the existence of a knower and something to be known. Descartes reversed the order and in doing so helped create what we call modernity.

Over the past few decades, many Christians—particularly those intrigued by postmodernism—have rightly questioned Descartes’ reversal. They have attempted to dethrone the idol of reason by pointing out the limits of rationality and questioning the human ability to achieve epistemic certainty, particularly about matters of theology. Unfortunately, in trimming away the underbrush they have failed to cut away the root of Descartes error: the faith in doubt.

Among these Christians, as well as among secular intellectuals, doubt about metaphysical truths—such as the existence and creative actions of God—has become viewed as a form of intellectual humility. Once considered evidence of a poor intellect, agnosticism and atheism are now treated as evidence of intellectual virtue.

Nothing could be further from the truth. This reliance on doubt requires that the doubter be the supreme judge of what can or cannot be known. Rejecting a dogmatic certitude about what is known in favor of a questioning attitude of whether something can be known with certainty merely shifts the idol of reason to a new location and gives it a more palatable, humble-sounding name. The doubters accept the limits of the human mind, embrace pluralism, and do not impose any one idea of truth upon others.

However when we put our trust solely in our own reason we either become dogmatic or skeptical, and even dogmatic in our skepticism. But when we set aside our self-idolatry and seek true epistemic humility we can discover that the only reliable foundation for reason is found in special revelation.

The only solid basis for our knowledge was revealed more than a thousand years before Descartes began to doubt. As the first chapter of John assures us, the Truth created all that exists:

In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things came into being through Him, and apart from Him nothing came into being that has come into being. In Him was life, and the life was the Light of men. The Light shines in the darkness, and the darkness did not comprehend it. (John 1:1-5)

Commenting on this passage, James Sire notes that this means “God in Christ is the Meaning of everything. He is the ultimate Reason of all Being—his own being and the being of the universe.”

Because Christ created all things, everything—all existence—is imbued with meaning. We only know any truths because he exists. Christians can doubt many things, but to question the existence of God—or even to consider it an intellectually respectable proposition—is to doubt the source of all meaning in the universe. Are we able to take the place of the Creator, constructing reality and meaning ex nihilo? 

We can deny God and retain an illusion of certainty. But there is only one indubitable foundation for knowledge—our reason and our ability to know is rooted in the person of Jesus Christ. We are not merely making claims about him; we are simply recognizing what cannot but be acknowledged when we truly humble our reason: that Christ is the Logos, the creator of all meaning and the fountainhead of all truth.

Joe Carter is web editor of First Things.