“形式永远追随功能”
不管是鹰击长空，还是苹果花开，是劳作的马，还是悠哉的天鹅，是枝繁叶茂的橡树，还是蜿蜒的溪流，是漂动的云朵，甚是东升西落的太阳，形式永远追随功能，而且这是规则。功能不变，则形式不变。花岗岩、沉寂的山丘，亘古未变；闪电般的生命，形成，而后死去，转瞬即逝。
生命在其表达中得以被认识、形式永远遵循功能，这是有机和无机的一切事物、形而下和形而上的一切事物、人类的和超人类的一切事物、头脑中一切真实的表现、心灵、灵魂的普遍规律。这是规则。
—— 路易斯·沙利文 《高层办公建筑艺术思考》
“Form ever follows function”
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 Sullivan 《The Tall Office Building Artistically Considered》