There seems to be a pattern in languages (in the broadest sense in the context of this article: a series of symbols that are evaluated or interpreted): a duality between first-order expressions and second-order expressions that have different purposes but paradoxically use the same symbols. A language also needs to represent information used in a capacity different from first-order expressions. A language evaluator (e.g., someone reading a sentence) needs the delimiters to switch between first-order and second-order purposes.