Whether it be the swee­ping eagle in his flight, or the open apple-blos­som, the toiling work-horse, the blithe swan, the bran­ching oak, the winding stream at its base, the drif­ting clouds, over all the cour­sing sun, form ever follows func­tion, and this is the law. Where func­tion does not change form does not change. The gra­nite rocks, the ever broo­ding hills, remain for ages; the light­ning lives, comes into shape, and dies in a twink­ling. It is the per­va­ding law of all things or­ga­nic and in­or­ga­nic, of all things phy­si­cal and me­ta­phy­si­cal, of all things hu­man and all things su­per­hu­man, of all true ma­ni­fes­ta­tions of the head, of the heart, of the soul, that the life is re­cog­ni­za­ble in its ex­press­ion, that form ever fol­lows func­tion. This is the law.

[Louis H. Sullivan; 1856 – 1924]