“Form follows Function.” A phrase coined by the late Louis Sullivan in 1896 in his article titled The Tall Office Building Artistically Considered. In reality, the phrase was “Form ever follows function”, and was based on Roman ideas of Vitruvius of architecture being solid, useful, and beautiful. There have been several other writings that followed in history on this subject based on this idea as well. “Ornament and Crime” comes to mind quickly. This modern idea developed in the late 19th and early 20th century in architecture and still has what I would call a stronghold in the profession and discipline. This statement essentially became the mantra of Modernism.
Source: Life of an Architect