<a href="http://en.wikipedia.org/wiki/Charles_Sanders_Peirce">Charles Sanders Peirce</a> (born 1839) explicitly declared his <a href="http://en.wikipedia.org/wiki/Existential_graph">Existential Graphs</a> (all three parts: Alpha, Beta, and Gamma) to be his *chef d'oeuvre*. This work on graphical logic began sometime in the early 1880's, and he continued to work on it until his death in 1914.