Our reality is based on categorizations spun from our minds. For a thing to be defined by science, it needs an objective identity. Something that makes it irrefutably unique. What makes a thing unique apart from the thing itself, are the words and symbols used to categorize it. But those words and symbols themselves can only be defined by other words and symbols. And reality would have it that everything is unique, for no parts are shared. And yet we insist of putting labels on things, and wonder why they don't fit.