I have a knife said George

 

It has a wooden handle

 

 

I have knife said Polly

 

It has a metal handle

 

 

I looked at them both and noted that I did not care what material the handle was made from

The blade was the most important part of the knife as without the blade would be a different thing and not a knife any more

The blade was its essential property and gives it its defining function

Plato and Aristotle believed this to be true

I have a knife said George

 

It has a wooden handle but no blade

 

It is therefore not a knife

 

 

 

I have knife said Polly

 

It has a metal handle but no blade

 

It is therefore not a knife

 

 

 

The item that we hold in our hands has no defining function and therefore does not exist

 

I handed both George and Polly two sharp blades but asked for the handles in return

Now that you possess the blades but not the handles do you each possess a knife

 

The siblings stayed silent and looked at me

The answer is no as you both once possessed handles and latterly you have been given blades

 

But neither broadly have a defining function

 

They only function together like our lungs and other organs

 

I gave George and Polly the handles but did not request the return of the blades

After a while they had both reconstructed their knives and handed them to me in exchange for a steam locomotive

I was too polite to refuse their offer