Writing systems have existed for thousands of years, but it was not until the early 20th century that linguists—and artists—began to systematically probe the relationship between writing and communication. In 1916 the linguist Ferdinand Saussure proposed that the form a language takes is arbitrary and unrelated to its meaning. A decade later, the French writer Henri Michaux explored these ideas in asemic writing—writing that resembles natural language but conveys no meaning. Since then, artists have developed personal systems of pictograms and glyphs with varying degrees of legibility and idiosyncrasy, often to explore a wide range of concepts. In the 1960s, for example, A.R. Penck drew inspiration from cybernetics, the study of systems, to derive a hieroglyphic-like system of signs, which he used to represent societal and metaphysical relationships. In the 1980s, Gu Wenda developed a system of meaningless ideograms that resemble traditional Chinese calligraphy. Given how fundamental writing is to cultures throughout the world, it is no surprise that many personal writing systems may verge on the purely calligraphic, as in the gestural paintings of Cy Twombly.