Wet Sidewalks and Odd Numbers

A short, playful essay titled "Wet Sidewalks and Odd Numbers" has been making the rounds on Lobsters and linking back to philcrissman.net. It has been reported that the piece riffs on Lewis Carroll-style dialogue—Achilles and the Tortoise in the park—to walk readers through a simple but satisfying logical point: if P implies Q and Q implies R, then P implies R. Charming? Yes. Pedantic? Also yes. But there's more here than cute prose.

The setup: a sidewalk, a sprinkler, and an "aha" moment

In the dialogue the Tortoise forces a tightly constrained world — no sprinklers, no buckets, just rain — and uses that contrived backyard logic to illustrate implication chains. Achilles objects, hedges, and finally concedes; the emotional beat lands when the transitivity of implication is spelled out and everyone nods like they were at a small, nerdy epiphany. The piece name-checks Douglas Hofstadter and Philip Wadler, and nods to Gödel-era playfulness. Allegedly, the author begins with an apology to Lewis Carroll; the tone is deliberately whimsical while the point remains rigorous.

Why programmers should care

Why should coders read a parable about puddles? Because implication in everyday language maps directly to function composition, type relationships, and proofs in programming languages and verification systems. The same transitivity that turns "wet sidewalk" into "cloudy sky" underlies how a compiler reasons about types, or how a proof assistant composes lemmas into a theorem. With formal verification and safe-by-design languages getting mainstream pushes, a gentle reminder that logic underpins our tooling is timely.

A brief, witty piece — not a manifesto, but a tidy refresher. It’s the kind of small, literary nudge that makes you smile and then want to check your invariants. If you like your logic served with a side of Carrollian banter, this one lands.

Sources: philcrissman.net, Lobsters