Final answer:
In formal languages, symbols must consistently refer to the same object to maintain precision, while in natural languages, words can have different meanings depending on context. Philosophers like Frege and Russell have contributed to understanding and reducing ambiguity in language.
Step-by-step explanation:
The question queries whether it's a rule of formal language that all instances of a symbol must refer to the same object. In the context of formal languages, such as those used in mathematics and logic, this is indeed a requirement for clarity and precision. Each symbol or term must have a consistent and unambiguous reference.
In contrast, natural languages often feature words that can have multiple meanings depending on the context. For instance, the English word "bark" can refer to the sound a dog makes or the outer covering of a tree. Philosophers like Gottlob Frege and Bertrand Russell have dissected language and its functions. Frege proposed translating sentences into a formal language to eliminate ambiguity, while Russell discussed definite descriptions to uniquely identify objects.
Despite the potential for multiple meanings in natural language, in formal languages, symbols are strictly defined to ensure that each occurrence references a single, specific object or concept. This is crucial for maintaining the accuracy and consistency required in fields such as mathematics and computer science.