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.
Too much variation to distinguish the two
There are too many exceptions to the definitions of languages and dialects to clearly distinguish them.
Languages and dialects cannot be neatly categorized as separate phenomena because none of the popular, scholarly, or sociopolitical definitions are sufficient.