Every human being believes something to be true that his senses have never confirmed. Christians do when they accept the existence of an immaterial, transcendent reality. Scientists do when they assume that laws can be universal without being tested universally. How we think we know things matters because how we know plays a significant role in what we believe to be true. Our culture’s theory of knowledge is at odds with biblical frameworks for knowing. To clarify the difference between these two approaches to knowledge, I will examine three methods of knowing: empiricism; rationalism; and one understood by Augustine that relies on the relationship between trust, belief, and knowledge.

Empiricism and Rationalism

Our culture’s theory of knowledge is based on a blend of two philosophical approaches: empiricism and rationalism.

The empiricist thinks that seeing is believing; that in order to accept something as true, a person must see, taste, touch, smell, or hear it. The empiricist remains skeptical about anything his senses have not “proven.” The disciple Thomas acts like an empiricist when he says, “Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe” (John 20:25).

By contrast, the rationalist thinks that human beings grasp truth by the mind alone and not by the senses. The rationalist remains skeptical about anything his mind has not “proven.” Euclidean geometry is an example of truth arrived at from a rationalist perspective. Euclid states that parallel lines go on infinitely in both directions and never cross. He says this not because he has seen lines go on infinitely without crossing but because his mind imagines, grasps, and then “proves” this to be true.

Empiricism and rationalism—in their radical forms—are mutually exclusive theories of knowledge. The empiricist would say to the rationalist: “You’ve never seen two lines go on infinitely and never cross, and neither have I. In fact, no one has seen this. I therefore reject your claim that parallel lines go on infinitely but never cross.” The rationalist would say to the empiricist, “Your senses have been mistaken on many occasions—your ears misidentify someone’s voice, your eyes misidentify someone at a distance. If your senses have been wrong only once, then you can’t rely on them. You can see and touch and hear all you like, but you must realize that your senses don’t get you any closer to the truth.”

These are extremes in the centuries-long historical debate about how human beings know things. What the empiricist and rationalist have in common, however, is (1) their conviction that their method of knowing gives them certainty about what is true and (2) their skepticism toward anything about which their method of knowing does not give them certainty.

Blending rationalism and empiricism, then, modern culture’s concept of knowledge is the conviction that “knowledge” brings indubitable certainty to the knower. Knowledge, therefore, is a special category—perhaps the only category—in which certainty is possible. Given this method of knowing, it is easy to understand why modern culture looks askance at something like “belief” in general and at Christianity in particular. Modern culture believes that those who “believe” (i.e., religious people) embrace a sub-par standard for deciding what is true and what isn’t—an inferior method of “knowing” that Christians call “belief” and which is bereft of certainty. “Belief,” modern culture would say, “is defined by a tenuous and insensible probability; it doesn’t count as knowing because there is no certainty. Outside of certainty, there are simply multitudes of opinions, all equally questionable. Those people who are willing to do the work, however, can have certain knowledge and don’t have to settle for spongy belief. Believing is for the lazy and naïve.”

Furthermore, modern culture conjoins its view of knowledge-as-certainty to a concept of progress passed down from the Enlightenment when rationalism and empiricism flourished—namely, that over time knowledge replaces belief. Physicist Stephen Hawking’s (1942-2018) commentary epitomizes this view: “The one remaining area that religion can now lay claim to is the origin of the universe, but even here science is making progress and should soon provide a definitive answer to how the universe began” (Hawking, 28). To Hawking, a rationalist who “spent [his] life traveling across the universe, inside [his] mind” (Hawking, 3), religious belief is a mere placeholder that provides temporary answers until scientific knowledge arrives with the facts. In Hawking’s way of thinking, science and religion (or knowledge and belief) are mutually exclusive categories, a view widely held today.

I would argue, however, that modern culture’s concepts of knowledge and belief, exemplified in Hawking’s work, are flawed. The modern formulations of these concepts are based in unrealistic methods of knowing that are not consistent with how humans behave and overlook the real and indispensable relationship between belief and knowledge. For every human being, from the physicist to the priest, knowledge is grounded neither in indubitable certainty nor in insensible probability. Rather, human knowledge is grounded in trust, which I will define here as a likelihood undergirded by reasonable criteria developed through personal experience that is too complex and nuanced to fully articulate. It is trust, then, that leads to belief and, ultimately, to knowledge.

In the late fourth century, Augustine of Hippo raised this very issue. Let us consider his analysis of the relationship between trust, belief, and knowledge.

Augustine’s Way of Knowing

Augustine of Hippo (354-430) was a North African theologian, citizen of Rome, Church Father, rhetorician, exegete, and bishop in the Roman Catholic Church. He became a Christian at age thirty-one and by age forty-three had written thirteen books reflecting on his journey through skepticism to faith. He titled these books Confessions, a work considered by many to be the first autobiography of Western civilization.

In Book VI of Confessions, Augustine, disillusioned with polytheism and other religions, finds himself drawing closer to Christianity. Reflecting on the many things that he believes and why he believes them, he writes,

Then, O Lord, you […] set my thoughts in order, for I began to realize that I believed countless things which I had never seen or which had taken place when I was not there to see—so many events in the history of the world, so many facts about places and towns which I had never seen, and so much that I believed on the word of friends or doctors or various other people. Unless we took these things on trust, we should accomplish absolutely nothing in this life.

Here, Augustine is realizing that much of what he thinks to be true is based on trust, not on first-hand experience. In order to comprehend the sort of common human experience that Augustine is describing, I propose the following working definitions of trust, belief, and knowledge derived from his thinking:

Trust is a state in which someone is willing to accept (and potentially act on) information as true because of the relationship between the information’s source/cause and the one who trusts. The concept of relationship here is essential because relationships establish expectations, commitments, and obligations that when mutually fulfilled build “trust.” If expectations, commitments, and obligations are not mutually fulfilled, then trust erodes. While we tend to think of relationships as primarily between people, I would argue that we also have relationships with our senses—we expect them to give us accurate information. When we correctly predict outcomes based on the information our senses give us, then we trust our senses more.

Belief is the conviction that something the believer cannot exhaustively confirm is likely to be true. Our senses give us information that our reason can process. It is reason, according to Augustine, “to which the facts communicated to the bodily senses are submitted for judgment” (Confessions, Book VII, 151). The essence of belief is that we may interact with what is true even though our understanding may be incomplete.

Knowledge is information, perspective, perception, or experience that affects the knower’s outlook and options in decision-making.

To transfer Augustine’s thinking to a common situation, consider the following. My eyes have given me decades of information about the world that when tested have proven reliable. For example, when I am about to cross the street, my eyes may perceive an oncoming car. My reason confirms that I am seeing a moving car and predicts that the car will eventually reach and then pass my location. Over many years, I have built a relationship with my eyes—my track record of seeing—and therefore, I trust my eyes that a car is approaching. I not only trust my eyes, but I believe my eyes even though they do not give me exhaustive information about the car, its speed, its makeup, or the mental state of the driver. My reason, then, processes the sensations of light and color presented to my eyes, and I conclude that I know a car is approaching.

In this scenario, I might also observe a distracted person walking toward the curb where I am standing. He does not see the oncoming car and thus does not engage in the actions of trust, belief, and knowledge with respect to the oncoming car, and so I grab his arm before he walks into its path. When I explain to him what I saw and why I grabbed his arm, however, he trusts me because he concludes it is reasonable to believe that I have acted in his best interest. He knows he has avoided a collision.

Augustine realized that his knowledge of just about everything was based on trust, not certainty. The significance of Augustine’s realization is this: if most of what humans know is based on trust, then believing is a very common action for all humans, not just the religious ones.

If this is true, then all of us should ask ourselves what our criteria are for trusting one thing and not another. I propose four criteria that most all humans employ, even if subconsciously: (1) The source of information about a scenario/claim has been consistently reliable over time, thus allowing us to make reliable predictions. (2) The scenario/claim itself is consistent with other things we know. (3) We have inarticulable knowledge (for example, feelings, emotions, complex rational judgments) that the scenario/claim corresponds to reality. (4) We are willing—or not willing—to pay the cost of believing in the scenario/claim.

Trusting, believing, and knowing are not neutral activities. The knower must make decisions about what he trusts and why, and he also must weigh the costs involved in admitting to himself or to others that he knows something.  Augustine recognized the costs associated with believing Christianity when he wrote the following:

I had prayed to you [God] for chastity, and said “Give me chastity and continence, but not yet.” For I was afraid that you would answer my prayer at once and cure me too soon of the disease of lust, which I wanted satisfied, not quelled. I had wandered on along the road of vice in the sacrilegious superstition of the Manichees, not because I thought that it was right, but because I preferred it to the Christian belief, which I did not explore as I ought but opposed out of malice. (Confessions, Book VIII, 169)

When we think that a belief will cost us (for example, our wealth, comfort, social status, or even the indulgence of baser instincts), we may suddenly become devoutly skeptical, telling ourselves that no one can “prove” the claim that will cost us more than we care to pay. Whereas when trusting only necessitates that we believe some obscure claim that costs us nothing, our objections are much less severe, as were Augustine’s when, before his conversion, he disbelieved biblical testimony while embracing claims from “friends or doctors or various other people.”

This rationale for skepticism is nothing new. Augustine writes in Confessions, “I began to think that the philosophers known as Academics were wiser than the rest, because they held that everything was a matter of doubt and asserted that man can know nothing for certain” (Confessions, Book V, 104). To someone committed to the wrong sorts of behaviors, skepticism is wonderfully convenient. And, our culture’s concept of knowledge-as-certainty that developed from rationalism and empiricism breeds skepticism about anything that is “uncertain.” If certainty is the essence of knowledge, and the skeptic claims axiomatically that nothing can be known for certain except those claims that are provable by an approved method of knowing, then all “unproved” claims are equally dubious.

Augustine’s realization about how humans “know” is significant because while he was exceptional in many ways, his humanity and approach to trust, knowledge, and belief exemplify experience common to every human being.

By contrast, the radical empiricist and radical rationalist advocate a method of knowing that does not align with common human experience, and, as such, is neither realistic nor reasonable. No matter what he says, the radical empiricist always believes that when he blinks, the world around him remains and that when he walks out of a room, the objects in the room continue to exist. The radical rationalist trusts the testimony of his senses as he looks both ways before crossing the street, even though he lacks a rational proof that his senses tell him the truth about reality.

Those who intend to be devoutly skeptical—that is, those who accept as true only what they can prove as certain—set an unlivable standard for themselves. The devout skeptic ought to consider that consistency demands he doubt uniformly and with equal intensity all unexperienced events, objects, and occurrences.


Augustine draws together an important relationship between trust, belief, and knowledge. Knowledge rests on belief and belief on trust. If Augustine is right, then we must acknowledge that we know things because of how and whom we trust. We do not know because we are certain. We know because we trust.

Both empiricists and rationalists think that they have formulated and embraced a higher standard for knowing, one in which certainty plays a key role. What they have actually formulated, however, are unrealistic models for knowing which neither they nor any other human can use and in which certainty plays no real part. Neither position addresses the complexity of human experience because both positions demand an oversimplification of human experience. Consequently, these positions are not particularly helpful, at least in their radical forms. If the ultimate function of knowledge is to help a human being navigate life, then radical empiricism and rationalism fail because they do not meet this end. They both fail to address how human beings live according to what they think they believe and know.

At this point, empiricists and rationalists might protest, “at least we aspire to know with certainty.” Whether their aspirational goal is merely pursued or actually attained, however, it doesn’t generate the kind of progress they think it does because the standard they champion is misaligned with how human beings actually operate.

Despite what our culture says, all human beings know things in the same way—in the way Augustine describes—whether Christian or not. Each person, at some point, must confront the question of who and what he will trust and why. For the Christian, a common set of questions must be reviewed daily: Will I trust the words of Jesus Christ? Will I trust his analysis of the human condition? Will I trust his solution? Will I trust him enough to follow despite what it may cost me?


Saint Augustine (author) and R. S. Pine-Coffin (translator). Confessions. London: Penguin Classics, an imprint of Penguin Books, 2015.

Hawking, Stephen. Brief Answers to the Big Questions. First U.S. edition. New York: Bantam Books, 2018.

This article first appeared in the Fall 2019 issue of Colloquy, Gutenberg College’s free quarterly newsletter. Subscribe here.