https://maximummathematics.com/books/foundational-mathematics/set-theory/russells-paradox/index.htmlSets are a powerful abstraction that allows us to collect a wide variety of objects into one structure. Typically, all objects within a set share some common characteristic other than mere inclusion in the set. They may be points on the plane, equilateral triangles, even numbers, or even fruits. As powerful as sets are, we haven’t given a formal definition of what a set is. We’ve been relying on an intuitive definition, and though it works well enough for our purposes, sooner or later the cracks start to show. Sometime around 1901, a mathematician named Bertrand Russell formulated his now-infamous paradox that seemed to dismantle the entire theory of sets. The scary thing about the paradox is that a lot of mathematical research and important results rested on the foundations of Set Theory. If Set Theory is wrong, are all results depending on sets wrong as well?Hugoen-US