 Two logicians working in the Boolean tradition carried out these steps. The first step was partially carried out by Augustus De Morgan (in De Morgan 1864). The second was carried out by C. S. Peirce (in Peirce 1885). Working entirely independently, Gottlob Frege carried out both steps simultaneously in his Begriffsschrift of 1879. The subsequent history for several decades is a branching structure, with numerous researchers working in different traditions and only partially aware of one another’s accomplishments.