What if Space and Time Are Just Tools We Invented?
The Philosopher Who Said Space Isn’t Real
In 1917, a German philosopher named Moritz Schlick (1882–1936) made a claim that sounded impossible. He announced that space and time — the background against which every event happens — are not real, objective things. They are more like human inventions, rules of measurement that we design and then treat as if they were part of nature. A few years earlier, Albert Einstein (1879–1955) had written that his new theory of relativity “removes the last vestige of physical objectivity from space and time.” Schlick was one of the first thinkers to explain what that meant and why it mattered not just for physics, but for how we know anything at all.
Schlick had trained as a physicist under Max Planck (1858–1947), and he was deeply influenced by an older tradition of philosophical physicists, especially Hermann von Helmholtz (1821–1894). These scientists thought that the real work of philosophy was to understand the latest science, not to sit in an armchair spinning stories about reality. Schlick took that mission seriously. He set out to show how our most basic ideas — truth, knowledge, space — shift when we look at them through the lens of modern physics.
From Blurry Images to Sharp Concepts
Before he tackled space and time, Schlick wrestled with a simpler puzzle: how does a raw sensation turn into a piece of knowledge? Imagine you see a dark shape moving toward you across a field. At first you have only a blur of color and motion. As it gets closer, you recognize it as an animal. Then you see it’s a dog. Finally, you know it’s your dog, Fritz. Each step is an act of recognition: you know the shape as an animal, as a dog, as Fritz.
Schlick called the blurry mental pictures you start with intuitions. They are direct sensory experiences — the smell of wood smoke, the afterimage of a bright lamp — but they are never crisp or precise. If you try to picture your father’s face right now, you might not be able to say whether he is frowning or just thinking. That’s because intuitions are signs of things, not copies of them. Helmholtz had argued the same point decades earlier: your perceptions are like place-holders that stand for something in the world, but they don’t resemble it.
To move from fuzzy intuition to genuine knowledge, Schlick said, you need concepts. Concepts are ideas with exact boundaries, like the notion of a triangle, an electromagnetic wave, or a chemical element. In his book General Theory of Knowledge (1918), Schlick borrowed a powerful tool from mathematicians: implicit definition. Instead of defining a concept by pointing at examples or listing features, you define it by the relations it has to other concepts. A “point” in geometry, for instance, is defined entirely by the axioms that say how points lie on lines and between other points. The axioms become the rulebook for what the concept means. Schlick believed that scientific concepts are built this way — they are defined by the network of laws they participate in, not by what they look or feel like.
A Rulebook for the Universe: Conventions
Now Schlick had a new problem. If concepts get their meaning from a rulebook, who chooses the rules? When Einstein’s special theory of relativity appeared in 1905, physicists realized that two different ways of describing motion — one with an absolute, invisible “ether” and one without — could account for exactly the same experiments. Schlick argued that the choice between them was not about what is true in the world. It was a choice of convention, like deciding whether to measure a table in inches or centimeters. Both descriptions work because they are physically equivalent; they differ only in the representational scheme, the language we use to talk about the data.
This insight exploded when Schlick applied it to general relativity. In Newton’s physics, space was a giant, rigid grid that sitting still, the same everywhere. You could measure the length of a rod, and that length was a fact about the rod, independent of where it was. But Einstein showed that gravity bends the path of light and changes the behavior of rods and clocks. If you measure a rod near a massive star, you may get a different length than someone measuring the same rod far away, because the very notion of “same length” depends on the gravitational field. The grid itself is affected by what is in it.
Schlick zeroed in on what survives all this shifting. If you imagine two observers using completely different coordinate systems, what stays the same? They will both agree that a fingertip touched a particular spot on a blackboard, that a light beam hit a certain detector, that the needle of a dial overlapped with a certain mark. Schlick called these point-coincidences — moments when two physical things meet in space and time. All measurements, he argued, are ultimately based on such coincidences. The rest — the grid, the coordinate lines, the “absolute space” — is scaffolding we build to keep track of them. As he wrote, any feature of a world-picture that does not contribute to the system of point-coincidences is not physically objective.
In other words, space and time as a fixed, independent background did not survive the new physics. What survived was a set of relations among events, captured by point-coincidences. Everything else was part of the representational frame, and we are free to choose whichever frame makes the description simplest. That was a radical conclusion: the “stage” on which the universe acts turns out to be something we partly construct.
The Circle That Wanted to Test Every Sentence
In 1922 Schlick moved to Vienna to take a prestigious chair in the philosophy of nature. He joined a group of thinkers — mathematicians, physicists, and social scientists — who met on Thursday nights to debate the foundations of science. They called themselves the Vienna Circle, and under Schlick’s leadership they became famous for a bold idea: the meaning of a statement is the method by which you could verify it.
Schlick called this the verifiability principle. If a sentence purports to describe the world, you must be able to say what experience would show it to be true — at least in principle, even if you cannot perform the test right now. The statement “there are mountains on the far side of the moon” was meaningful because one day someone might fly around and see them. But a sentence like “the universe is made of an invisible, undetectable substance” was, by this standard, empty noise. According to the Vienna Circle, many old philosophical puzzles were really just confusions about language — they looked like meaningful claims but failed to make contact with any possible experience.
In his later work, Schlick refined this picture. He came to think that the rules governing meaning are like the rules of a game. A language has grammatical rules of two kinds: internal rules that say how words combine with each other (like the rules of chess), and application-rules that connect words to observable situations (like the rule that shows you how to move a chess piece). When you say “here now white” while pointing at a patch of snow, you are following an application-rule. The meaning of the sentence is not some ghostly thought inside you; it is the role the sentence plays in the whole system of rules. Schlick thought this insight could dissolve famous problems, like the claim that only your own mind exists (solipsism). The solipsist, he argued, is really proposing a new grammatical rule disguised as a fact — and once you see that, the mystery evaporates.
Why It Still Matters: What’s Real and What’s a Rule
Schlick never learned a computer, but his ideas are close to something you already do. When you play a video game, the “space” inside the game exists only because the programmers set up a coordinate system and rules for how objects relate to it. A character “moves three meters” because the code says so; the meter is not a real distance, it is a conventional unit in a representational scheme. The only real events are the pixels lighting up on the screen — those are like point-coincidences. The game’s space is a tool, not a thing.
Schlick’s thought helps us ask sharper questions about our own world. When scientists talk about “cosmic time” or “gravitational waves,” they are using concepts that are defined implicitly by the equations of general relativity. Those concepts are real in the sense that they organize point-coincidences into a powerful, unified picture. But the picture’s grid lines, its units, its coordinate choices — those remain conventions, as Schlick insisted. Distinguishing what belongs to nature from what belongs to the language we use to describe nature is still one of the hardest jobs in philosophy.
Schlick’s own story ended abruptly. In 1936, a troubled former student shot him on the steps of the university. The Vienna Circle scattered, but its influence already ran deep. Today, whenever a physicist says that time is not absolute, or a linguist analyzes meaning as rule-governed use, a thread leads back to Moritz Schlick — the physicist turned philosopher who asked whether space and time are out there, or whether they are just our finest tools.
Think about it
- Two mapmakers draw completely different maps of your neighborhood that both work perfectly — they get you where you need to go. Does a “real” neighborhood exist independently of the maps, or is the neighborhood itself just a collection of points people agree on?
- You feel time passing second by second, but a physicist says time is only what clocks measure. Who is right, and what could you point to that would settle the dispute?
- If the space in a video game is just a set of rules, and the space you walk through in your daily life is also described by rules and measuring instruments, how do you know that the space you live in is any more “real” than the game’s?
