What is the fallacy of thinking that things are separate when infact they all add up into one single entity, what is this folly in thought called?

Every Little Helps

Nasrudin loaded his ass with wood for the fire, and instead 
of sitting in its saddle, sat astride one of the logs. ‘Why don’t you sit in the saddle?’ someone asked.

‘What! and add my weight to what the poor animal has to carry? My weight is on the wood, and it is going to stay there.’

The fallacy demonstrated in the story of Nasrudin and his ass is a misunderstanding of how weight distribution works, illustrating a failure in logical reasoning. Nasrudin believes that by sitting on the wood rather than directly on the saddle, he is not adding additional weight for the animal to carry. This reflects a cognitive bias or misunderstanding known as the "composition fallacy."

The composition fallacy occurs when someone assumes that what is true of a part is also true of the whole. In this context, Nasrudin incorrectly believes that because his weight is distributed on the wood rather than directly on the ass, it is somehow separate from the total weight being carried. In reality, whether he sits on the wood or directly on the saddle, his weight is still added to the total burden of what the animal must carry. His reasoning fails to account for the fact that all the various components (the wood and his body) combine to form a single, cumulative load on the ass. This illustrates poor logic as he fails to properly assess the situation holistically.