Ruth Barcan Marcus

Ruth Barcan Marcus, born Ruth Charlotte Barcan, was an American academic philosopher and logician, born in 1921 and died in 2012, best known for her work in modal and philosophical logic. She developed the first formal systems of quantified modal logic and in doing so introduced the schema known as the Barcan formula, and also introduced the now-standard box operator for necessity. Publishing originally as Ruth C. Barcan, she has been described as one of the twentieth century's most important and influential philosopher-logicians, and the philosopher Timothy Williamson wrote in a 2008 celebration of her career that many of her main ideas were not only original, clever and influential but true.