> One might say who cares if they don't define it? Well, if you don't define it, there's no point in discussing whether it exists, how it came to be, or what it

> One might say who cares if they don't define it? Well, if you don't define it, there's no point in discussing whether it exists, how it came to be, or what it comprises. This is not how we normally treat other concepts, even in physics or mathematics. Concepts can exist and even be studied for a long time while lacking a rigorous definition. For example, a truly rigorous and satisfying definition of natural numbers probably dates from the 19th century. Does that mean that people before this shouldn't have discussed natural numbers? For another example, the Dirac delta function was used in the study and teaching of QM while not being very well defined as a mathematical object (it's not an actual function, for example). In general, most interesting concepts begin life as some kind of vague intuition, and it often takes significant study to create a formal definition that captures the intuition well. This applies to any kinds of concepts, even in mathematics.