Form follows function is a principle associated with 20th-century modernist architecture and industrial design which says that the shape of a building or object should primarily relate to its intended function or purpose.
The architect Louis Sullivan coined the maxim, although it is often incorrectly attributed to the sculptor Horatio Greenough (1805 – 1852), 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, venustas – that is, it must be solid, useful, 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. 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."