What Can You Really Know? The Philosopher Who Split Experience in Two
A Red Ball and a Big Question
Imagine you are looking at a shiny red ball on a table. You are absolutely sure you are seeing redness and roundness. But would you be just as certain that it’s a real ball and not a dream? In the 1920s and 1930s, the American philosopher C.I. Lewis (1883–1964) built an entire theory of knowledge on that difference. He wanted to know: what part of our experience can we trust completely, and how do we turn that into reliable beliefs about the world?
Lewis was a Harvard professor who studied logic and the way we know things. He started his career re‑thinking the rules of “if‑then” thinking, but his biggest idea was a view he called conceptual pragmatism. The name is a mouthful, but the core picture is simple. Lewis said that whenever we perceive something—like a ball—our mind is doing two things at once. First, it receives raw, unprocessed sensations, which he called the given. Second, it interprets those sensations using concepts we bring to the table, like “red,” “round,” or “ball.” The given is the part we cannot be wrong about; the interpretation is the part we can. Everything we claim to know, Lewis argued, is built from that mixture.
The Given: Raw Feels You Can’t Get Wrong
What is the given, exactly? Lewis described it as the immediate sense qualia (the felt qualities of experience) that appear to you right now: the particular redness you see, the coolness you feel, the hum you hear. These are not beliefs about objects. They are private, indubitable, and not something you can be mistaken about. You might be wrong that a red ball exists, but you cannot be wrong that you seem to see a red patch. Lewis called this awareness incorrigible — impossible to correct. It is certain, but in a way he thought didn’t count as “knowledge,” because knowledge always involves the risk of error.
To communicate the given without turning it into an object-claim, Lewis introduced the idea of expressive statements. When you say, “It seems as though I am seeing a red round thing,” you are using language in an expressive way. You aren’t talking about a thing called a red ball; you are simply conveying the character of your present awareness. This matters because, for Lewis, expressive statements can be true even when our objective beliefs are false — and they form the bedrock of all justification.
Lewis believed that the given never appears all by itself in everyday life. We are always already interpreting it. But, he said, you can catch a glimpse of pure givenness in an aesthetic attitude — when you get absorbed in a sound or a color without trying to label it, like losing yourself in a symphony’s texture before you think, “That’s a violin.” That raw absorption, he thought, is what the given feels like.
Concepts Are Like Maps You Draw
If the given is just a silent rush of sensations, how do we ever get to the belief that there’s a ball in front of us? Lewis’s answer: our mind brings a concept to the experience, and a concept is a kind of prediction kit. When you apply the concept “ball,” you automatically expect that if you seem to reach out, you will seem to feel something round and bouncy; if you seem to squeeze, you will seem to feel resistance. These expectations are what Lewis called terminating judgments — “if I do this, then I will have that experience.” Together, they spell out the meaning of the concept.
Because concepts contain predictions, they can be confirmed or disappointed by further experience. That makes them fallible. Lewis argued that we don’t discover our basic concepts the way we discover facts about the world. Instead, we legislate them — we adopt a set of rules for sorting our experience, much like deciding to draw a map with particular symbols. That decision is a priori, meaning we don’t justify it by looking at evidence. It’s a choice we make before testing anything. Its goodness is measured not by truth or falsity but by pragmatic criteria: how simple, convenient, and useful the resulting system of beliefs turns out to be.
This is where Lewis’s pragmatism shines. He said that principles like “Balls are round” or even the truths of logic are analytic — true by virtue of the meanings we have built into our concepts. We can know them a priori, simply by reflecting on the definition we’ve given. If experience ever pushes us to abandon a concept (say, we keep failing to spot unicorns), we don’t prove the concept false. We just decide it’s no longer useful and swap it for another, the way you might stop using a poorly drawn map and draw a better one.
Memory, Probability, and the Hunt for Certainty
So far, so neat. But Lewis faced a problem that keeps any empiricist up at night: what grounds our belief that the future will behave like the past? When you expect the ball to feel smooth, you’re relying on memories of past touch-experiences. Memory, however, is not the given. You don’t have direct, incorrigible access to the past; you have a present sense of having experienced something, what Lewis called mnemic presentation. Lewis argued that what we seemingly remember is prima facie credible — believable on its own, unless we have special reason to doubt it. It doesn’t need to be certain; it just needs to be initially believable enough to get probability off the ground.
Probability, for Lewis, was not about how often something happens in the actual world. It was a logical relation between a claim and the data we have. If your present sensation and your recollections make it reasonable to expect something, then that expectation is probable to that degree. The catch is that all probability must eventually rest on premises that are certain — otherwise we face an infinite regress where nothing is ever really probable. The given, being certain, serves as that ultimate anchor. Our recollections, though not certain, get their credibility from a basic principle that we are justified in trusting them until shown otherwise.
Lewis then wove these threads together with the idea of congruence. A system of beliefs is congruent when each belief would be more probable if the others were true. A mature body of knowledge about the world hangs together like a tightly laced net. The net gets its initial strength from threads tied directly to the given and to memory, but the mutual support among beliefs can raise their credibility high enough for practical action — high enough to be called knowledge, even if not absolutely certain.
The Myth of the Given? The Big Debate That Followed
Lewis’s picture of knowledge was elegant, but it drew powerful fire from three younger philosophers. Willard Van Orman Quine (1908–2000) attacked the distinction between analytic and synthetic truths that Lewis relied on. Quine argued that no statement is absolutely immune to revision by experience. Even logical and mathematical principles, he said, are part of the same web of belief as ordinary facts, and surprising experiences could in principle lead us to tweak them. Lewis replied that logic and definitions can indeed be revised, but only on pragmatic grounds, not because experience shows them false. The a priori doesn’t get disproven; it gets exchanged for a more convenient tool.
Wilfrid Sellars (1912–1963? actually 1912-1989, I’ll put 1912–1989) called the given a “myth.” He argued that awareness of something as simple as a red patch already requires conceptual abilities learned in a social practice of giving and asking for reasons. You can’t step outside all concepts to point at a bare sensation; any description smuggles concepts in. Lewis countered that the given doesn’t need to be described in conceptual terms to be experientially present — but Sellars’s challenge forced epistemologists to rethink what it means for a belief to be “directly” justified.
Nelson Goodman (1906–1998) raised a different worry about Lewis’s regress argument. Why must probability rest on certainty, he asked? Couldn’t some starting beliefs simply be initially credible to some small degree, supporting each other as a system, without any of them needing to be certain? Lewis answered that if no ground is certain, we confuse justification with future verification, and we lose touch with the reasons that make a belief warranted right now. This debate about foundationalism versus coherentism — whether knowledge needs a rock‑bottom given or can float as a web of mutually supporting beliefs — dominated epistemology for the rest of the 20th century.
Why It Still Matters: Are You a Builder or a Receiver?
Lewis’s ideas aren’t just dusty museum pieces. Every time you trust your senses while knowing you could be wrong, you’re living inside his picture. When you say, “It looks like it’s raining, but I’d better check,” you’re distinguishing between the given (the gray light, the streaky window) and the interpretation (rain). When you learn a new word, you’re adopting a concept that bundles predictions about future experience — the same kind of a‑priori legislation Lewis described.
The fight between foundationalists and coherentists still echoes. Can you ever point to a pure “this is just how it feels” that you don’t shape with language or culture? Or does everything you notice get filtered through the concepts you already have? Lewis thought we could walk that line: we are active builders who nonetheless touch a non‑conceptual given that keeps our maps anchored to reality. Whether he was right remains a live question. But he gave us a vocabulary for noticing the difference between raw experience and the stories we tell about it — a difference you can pay attention to right now, just by looking at that red ball (or whatever’s in front of you) and wondering where the sensation ends and the thought begins.
Think about it
- If you and a friend both say an apple is “red,” but your inner red‑feeling is what your friend would call green, does it matter as long as you both agree which fruit is the red one?
- Try to notice a pure, unlabeled sensation — a sound, a smell, a patch of color — without silently naming it. Is it possible? What does your mind do first?
- If every memory is potentially mistaken, can you be sure that anything you remember from five minutes ago really happened? How would you know?
