Theseus' Paradox: Does Modifying A Car Turn It Into Something Different?

Photo: Nitto

The Theseus’ Paradox asks the question: if you’ve replaced every part of something, is that something still fundamentally the same, or has it become a new thing altogether? Let’s talk about how this applies to modified cars.

You’ve probably heard this thought exercise before, likely in reference to George Washington’s axe. The question goes something like this: if the axe’s handle and head have both been replaced, how can it still be George Washington’s axe?


Though many don’t realize it, car enthusiasts talk about Theseus’ Paradox all the time. It’s an especially common topic in the off-road scene, where enthusiasts turn their Jeeps into buggies that share almost no parts with their donor vehicles. “That thing has no Wrangler parts left on it, so how can it be a Wrangler buggy?” many ask. And it’s a fair question.

Take the badass “Evo1" off-road racer in the top image and video above. Piloted by Mel Wade of Off-Road Evolution, this thing’s got a 408 cubic-inch Hemi V8 under the hood, a 727 automatic transmission, brand new axles, a completely new suspension, a gutted interior, new sheetmetal, new bumpers—I could go on, but suffice to say: this vehicle shares very, very little with the Wrangler on which it is based, sans the frame, which you can bet has at least been reinforced.

So that leaves the question: is this still that same Wrangler Mel picked up all those years ago in 2006? If your initial answer is “yes,” then answer this:

If we took all the parts Mel removed from the 2007 Wrangler to build the rig you see above—the powertrain, suspension, bumpers, interior, fenders, etc.—and put them on a different frame, would that also be Mel’s Wrangler? If so, how can we have two things with the same “identity?”


And that’s really what this question is all about: identity. It is the core state of being that transcends time, remaining impervious to outside influence.


This question about how modifying a vehicle changes its identity is something that’s been bugging me for years. I recall putting a lift kit on my 1992 Jeep Cherokee—a vehicle that I have held onto for sentimental reasons, as it was my first car and I love it dearly.

My concern was that with the new suspension and tires, the car would accelerate, brake, handle and sound differently, making the Jeep feel less like that janky burgundy XJ I bought in the Virginia stadium parking during my sophomore year in college and more like a completely different vehicle. More importantly, all those parts that once comprised the Jeep back when I bought it would be tossed into the trash.


Luckily, after the lift, I found that, in my head, this now rough-riding, taller, louder, slower and worse-handling red Jeep with aftermarket components was still my darling because my brain continued to assign the new conglomerate of parts the same “identity” as the old assembly of parts. Changing the suspension wasn’t enough for me to redefine the Jeep as something different.

Dropping a new engine into my 1992 Jeep after blowing up the old four-liter.

Then, last year, I blew up my Jeep’s motor in a freak off-roading accident (actually, I just drove into a mud hole too quickly), and my heart sank.

To me, that 250,000-mile engine, now with two rods sticking through the oil pan, was the heart of that vehicle. I worried that swapping in a new engine would make me lose my attachment to the Jeep and that I’d have no reason to keep the rusty pile around anymore. Had that mud hole killed my “first Jeep” forever on that fateful day last November?


After driving the Jeep with the new engine, I must admit that I feel like part of my “first Jeep” died that day last fall. I can tell by the feeling I get when I turn that ignition switch and punch the gas pedal down on a country road. I’m no longer cheering on Old Faithful under the hood: there’s a new guy in play and it just doesn’t feel the same.

Me refreshing the old engine just a few months before it met its ultimate demise.

But I say “part of” because even if the suspension and engine are all new, for some reason, the “soul” of my first Jeep remains embedded in this new grouping of parts. Maybe it’s the interior—where I spend all of my time—with its familiar comfy cloth burgundy seats and shallow dashboard that make me feel at home.

Or maybe it’s the flaws that help my mind assign the identity of my first Jeep to this new grouping of bits—flaws like the hole in the passenger’s seat, the little tree seed that’s been stuck in the dash vent since I bought the Jeep, the gas gauge that doesn’t care how much fuel is in the tank, the missing clear coat, the unpainted fender and the rattle-canned header panel.


Or maybe it’s just the fact that the body is the same. Honestly, I can’t put my finger on it. If someone put a pair of new rods in my old engine and slapped that into another Jeep, would I feel as strongly about that other boxy XJ? I’m not sure.

And so sadly, this post has to end with a question: what part or parts, when removed, change the very identity of an automobile? Is it the frame? The title and VIN? The interior? The body?


Only your heart will know the answer.

Update: Quite a few readers have pointed out to me that Regular Car Reviews discussed this very topic in its latest Fox Body Mustang video, so definitely have a watch:

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About the author

David Tracy

Sr. Technical Editor, Jalopnik. Always interested in hearing from auto engineers—email me. Cars: Willys CJ-2A ('48), Jeep J10 ('85), Jeep Cherokee ('79, '91, '92, '00), Jeep Grand Cherokee 5spd ('94).