Form follows function is a principle of design associated with late 19th and early 20th century architecture and industrial design in general, which states that the shape of a building or object should primarily relate to its intended function or purpose. The architect Louis Sullivan coined the maxim, which resumes Viollet-le-Duc's théories : a rationally designed structure may not necessarily be beautiful but no building can be beautiful that does not have a rationally designed structure. The maxim is often incorrectly attributed to the sculptor Horatio Greenough (18051852), whose thinking mostly predates the later functionalist approach to architecture. Greenough's writings were for a long time largely forgotten, and were rediscovered only in the 1930s. In 1947, a selection of his essays was published as Form and Function: Remarks on Art by Horatio Greenough. Sullivan was Greenough's much younger compatriot and admired rationalist thinkers such as Thoreau, Emerson, Whitman, and Melville, as well as Greenough himself. In 1896, Sullivan coined the phrase in an article titled The Tall Office Building Artistically Considered, though he later attributed the core idea to the Roman architect, engineer, and author Marcus Vitruvius Pollio, who first asserted in his book De architectura that a structure must exhibit the three qualities of firmitas, utilitas, venustasthat is, it must be solid, useful, and beautiful. Sullivan actually wrote "form ever follows function," but the simpler and less emphatic phrase is more widely remembered. For Sullivan this was distilled wisdom, an aesthetic credo, the single "rule that shall permit of no exception." The full quote is: 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.