Composition / Division
Logical fallacyComposition: assuming what is true of the parts must be true of the whole. Division: assuming what is true of the whole must be true of each part.
An everyday example
“Every player in the squad is excellent, so the team must be excellent.”
The same move in this debate
“Some vegan products are ultra-processed, so a vegan diet is an ultra-processed diet.”
Where this appears
The argument moves from 'most plants on Earth are inedible to humans' to the suggestion that eating plants as a diet is harmful. It treats a fact about plants as a whole category as if it applied to the specific plants people actually eat. Those are a small, long-domesticated subset chosen precisely because they are edible.
Infers the cost of the whole diet from its most expensive components, which are also its most optional ones.
Infers that the diet is ultra-processed from the fact that some products available within it are. Meat substitutes are a small and optional part of what most vegans actually eat.
Reasons from the negligible effect of one person to the negligible effect of the group. The aggregate is precisely what moves production, and it is composed of nothing but those individual decisions.
The claim draws a conclusion about individuals, that eating meat makes a person live longer, from averages across whole countries. A pattern among nations does not transfer to the people within them, least of all to well-fed individuals choosing between planned diets.
Takes a finding about one animal food and treats it as a defence of animal foods generally. At most it supports eating some fish, and says nothing about the farming of pigs, chickens or cattle.
Reasons from the ineffectiveness of one person to the ineffectiveness of many, when the collective shift consists of nothing except those individual decisions.