Monday, February 20, 2006


I have some ideas that are still congealing in my mind. I am thinking about a certain ontological problem. Say you have a thing that is composed of a bunch of parts, like a car. Say you replace a wheel. The car is still the same car. Say you replace a couple more parts. The car is still a car. But after you replace enough parts, the car is no longer the same car that we started with. But when does this change happen.

I am pretty sure this is a classic ontological problem. If anyone knows the answer, chime in!


Blogger Irina Tsukerman said...

Actually... I think that as long as you're only replacing small parts, it's still the same car. But if you had to replace the entire skeleton, it would probably no longer be the same car.

February 20, 2006 9:43 PM  
Blogger B. Spinoza said...

In reality everything is one. Things are distinguished only by the fact that the human mind distinguishes one object from another. So to answer your question, if you or most people wouldn't consider this car as the same thing then it is considered a different thing. It's generally considered the same thing if the proportions of the object remain the same.

February 21, 2006 4:40 AM  
Blogger e-kvetcher said...


My point is: what if you eventually replaced all the parts one by one, one small part at a time. Imagine there is no skeleton. The car was just an example.


I have to think about what you are saying. It reminds me of the koan, if a tree falls in the forest and there is no one to hear it, odes it still make a sound?

February 21, 2006 4:53 AM  
Blogger Stevin said...

The change occurs when a foreign part is introduced.
The car remains the same car as long as the parts introduced are compatible and useful to the car.
However, once airplane wings and anvil bumpers are introduced, it becomes something else entirely.

February 21, 2006 9:04 AM  
Blogger Tobie said...

There was a whole section on this in Leo Katz's book "Ill-Gotten Gains", which is my current "smart" reading. Basically, he raises a number of paradoxes with this general idea. Suppose that your brain was going to be transferred to another body. If this was done all at once, everyone would agree that "you" are the new body. But if it is done sliver by sliver over the course of months, at every stage, you will think that "you" is the person with the old body- EVEN when the entire brain has been transferred to a new body. He doesn't have an explanation for why or how people think that way, he just uses it as an analogy for similar corporate restructuring.
So I guess, in your car exsmple, since the change is being done gradually, at the end it is the same car. Sort of like an army unit- after ten years, it may have none of the same people it did before, but because this wasn't a sudden transformation, it still is the same unit (pretending that there is no consistent external structure).

February 21, 2006 9:45 AM  
Blogger e-kvetcher said...


I am not sure we're talking about the same thing. The car analogy may be confusing more than helpful.

Imagine two watches that come off the same assembly line. They are identical, but each one is a separate object; it has it's own identity.

Now say you take one part of the watch, and replace it with another part from the second watch. Is it still the same watch, just with one updated part? Now keep doing it until you've replaced all the parts.

PS. Good to see your blog is up again!

February 21, 2006 11:12 AM  
Blogger e-kvetcher said...


I think you're getting the gist of my question. The army unit problem is in that vein of reasoning. However, the relationship is much more of an associative than aggregative. See my response to Stevin.

I'll check out this Katz book too. I think you may have mentioned it in a previous post/comment?

February 21, 2006 11:15 AM  

Post a Comment

<< Home