Are Mandarin and Cantonese individual languages, or are they dialects of Chinese? Questions like these would be easier to answer if dialects and languages were easy to define, but linguists still disagree on the difference between the two.
There is too much variability in the way each is described to divide them
There are too many exceptions to the definitions of languages and dialects to clearly distinguish them.
The excessive variation in definitions means they cannot be differentiated
Languages and dialects cannot be neatly categorized as separate phenomena because none of the popular, scholarly, or sociopolitical definitions are sufficient.