Who Ordered the Synthetic A Priori?

Small chat about the structure of the world

Our two characters: (because what’s better than a great conversation?)

Milo Cantwell, a jazz musician, alto saxophonist, instructor in improvisation at Harvard
Adrian Vale, a mathematician specializing in logic and the foundations of physics

Setting:

A corner table at The Plow & Stars, Cambridge, on the day after Thanksgiving. The air blowing in when someone enters carries a mild scent of wet pavement and the echo of a distant Red Line train rolling over the bridge. It’s exceptionally warm. A jazz trio is warming up—upright bass, brushed drums, muted trumpet—arranging their music under muted lighting.

The bar is full of scattered conversations: two graduate students arguing about whether all knowledge is science knowledge in the corner (obviously they’re Liberals); a couple on a first date trying too hard (obviously they’re Conservatives); an older professor-looking type reading a physical newspaper with a beer and staring into the distance (who knows what he is!).

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Milo enters first, balancing a saxophone case and wearing a deep plum scarf even though the night is quite warm for scarves. His scarves are like talismans—he owns too many—and this one’s frayed edge testifies to a long-ago breakup he never quite recovered from. He orders a rye Manhattan, the kind a musician drinks not because he likes them but because he likes the ritual: the slow cherry drop, the glass fogging slightly at the rim. Ritual fills the spaces where religion used to live.

Adrian arrives soon after, carrying a slim black backpack filled with two identical blue shirts he bought that afternoon at Uniqlo—one to replace the one he was wearing, the other to keep on reserve. Adrian buys the same shirts partly from aesthetic minimalism, partly because choosing feels like a metaphysical risk. He orders a seltzer with lime because the idea of blurred faculties makes him uneasy; clarity is not just an intellectual value for him but a moral one.

Milo: (smiling) You look like you’ve just proved a theorem that disappointed you.

Adrian: I taught a seminar. Same thing.

They both laugh in obligation and sit.

Milo: How was your Thanksgiving?

Adrian: OK. My sister came over.

Milo: I’ve been thinking about what you wrote in that long text message just before the holiday. You still deny Russell had any Kantian inclinations.

Adrian: Not inclinations. Coincidences. Convergences forced by physics and logic. But no shift in metaphysics. No “warming up to Kant.”

Milo: Haha. That’s just wrong.

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The trio on stage begins their set. Milo briefly goes into auditory mode. He tilts his head as though he’s listening for a pattern only he can hear.

Milo: Listen to that trumpet. You hear it as a melody, right? Not as scattered vibrations hitting your ear.

Adrian: Of course.

Milo: But the world doesn’t give you melody. It gives you pressure waves. You synthesize the melody. Your mind brings the unity.

Adrian: (shrugs) The auditory cortex groups similar frequencies. It’s physiology, not metaphysics.

Milo: For Kant—and for me—the structure of experience doesn’t arise from outside. The subject puts it there. That’s how a melody works.

Adrian: Milo, you’re making a mistake. What’s necessary for the human mind may not be necessary for mind in general, nor for the world. Russell understood this. That’s why he rejected Kant: Kant smuggles psychology into ontology.

Milo: That’s early Russell, by the way. But I just disagree. Kant isolates the structural contribution because he’s looking for universals that make experience possible in the first place—not “human quirks,” but general conditions.

Milo says this in a gentle way. It’s in fact deeply personal. He has always mistrusted the idea that the mind is merely a passive receptive.

Adrian: But even if Kant is right about the “structure of experience,” it doesn’t follow he’s right about the “structure of the world.”

Milo: Isn’t that exactly the question? Can we peel them apart?

Adrian swallows. His parents divorced over a philosophical disagreement—his mother a successful artist, his father a physicist. He’s spent years trying to keep both worlds separate.

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Adrian pulls a small notebook from his pack and shows Milo a quote he copied earlier that day.

“What we know about the physical world is only its structure, not its intrinsic character.”
—Russell, Human Knowledge: Its Scope and Limits

Adrian: See? Structure, not essence. That’s Russell’s view. Pure objectivity.

Milo: (grins) Ah, but structure relative to what? You know that Russell provides the backdoor to Kant.

Adrian: (frowning) Explain.