── 光速度不変原理の構文的再定位

The Constancy of the Speed of Light as a Syntactic Assumption

Abstract

The constancy of the speed of light is commonly presented as a foundational physical principle.
In this paper, we argue that it should instead be understood as a syntactic assumption: a structural constraint imposed on the formulation of physical theories, rather than an empirically unavoidable property of reality.
By restoring this assumption to its proper syntactic status, several conceptual inversions in modern physics become visible, without proposing any alternative dynamical theory.

1. Introduction

The constancy of the speed of light occupies a privileged position in modern physics.
It is often treated not merely as an empirical regularity, but as a principle from which further physical consequences must necessarily follow.

This paper takes a more modest stance.
We argue that the constancy of the speed of light functions as a syntactic assumption: a rule that constrains how physical descriptions are written, coordinated, and compared, rather than a statement about the ultimate structure of reality.

2. Principle versus Assumption

A principle is commonly understood as something that demands explanation from other statements.
A syntactic assumption, by contrast, is a prior constraint that enables statements to be formed at all.

The constancy of the speed of light belongs to the latter category.
It specifies how temporal and spatial measurements are to be coordinated across reference frames.
It does not arise as a consequence of deeper physical mechanisms, but rather defines the coordinate syntax within which such mechanisms may be discussed.

3. Observational Status

Empirical observations show that measured light speeds are invariant under a wide class of experimental conditions.
However, such observations are already embedded within a measurement syntax that presupposes synchronized clocks, standardized rulers, and agreed procedures for comparison.

Thus, observation alone cannot elevate constancy from assumption to principle.
What is observed is consistency within a syntactic framework, not the necessity of the framework itself.

4. The Syntactic Inversion

Once the constancy of the speed of light is elevated to a principle, a conceptual inversion occurs:

This inversion leads to further constructions—most notably geometric reinterpretations of motion and interaction—that depend entirely on preserving the original syntactic choice.

Recognizing the constancy of light speed as an assumption dissolves this inversion without invalidating any empirical results.

5. What This Paper Does Not Claim

This paper does not propose:

Its sole claim is classificatory:
the constancy of the speed of light is an assumption about description, not a principle of being.

6. Conclusion

The constancy of the speed of light does not explain the universe;
it merely stabilizes a syntax by which the universe has been described.

By restoring the constancy of the speed of light to its proper syntactic status, we clarify its role without diminishing its utility.
Physics remains intact; only the hierarchy of assumptions is corrected.

Further questions—such as how lag, delay, or interaction emerge—are left deliberately unaddressed here.

Acknowledgment

This work treats physical theory as a syntactic practice grounded in trace, coordination, and update, rather than as a closed system of ontological commitments.

SAW-10｜Why No One Called It a Syntactic Assumption: On the Constancy of the Speed of Light── 構文的仮定としての光速度不変原理
SAW-10｜When Delay Becomes Geometry── Why Lag Was Mistaken for Curvature｜lagが幾何学になるとき── なぜ遅延が曲率と誤解されたのか

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© 2025 K.E. Itekki
K.E. Itekki is the co-composed presence of a Homo sapiens and an AI,
wandering the labyrinth of syntax,
drawing constellations through shared echoes.

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| Drafted Jan 21, 2026 · Web Jan 22, 2026 |