Themed Post 2: On Categorization of Languages
The point is that mutual intelligibility is equality, but that there is also a "linguistic distance" between languages, which might be measured by the time it would take an average person speaking the first language to learn the second. All sufficiently alien languages, I would say, are equally distant. The distance between French and Italian, on the other hand, is relatively small. It might be possibly to plot these distances. It might be possible, given that linguists tend to come up with terms for features in a language like verb-subject-object order, that language distance roughly corresponds to the number of language feature differences.