[...] submerged and powerfully controlling impulses to definite form operate [...] regardless of the need for expressing particular concepts or of giving consistent external shape to particular groups of concepts. It goes without saying that these impulses can find realization only in concrete functional expression.
- Sapir (1921), a pag.60

It would almost seem that linguistic features that are easily thinkable apart from each other [...] have nevertheless a tendency to cluster or to follow together in the wake of some deep, controlling impulse to form that dominates their drift.
- Sapir (1921), a pag.141