Christine Ladd-Franklin is often hailed as a guiding star in the history of women in logic—not only did she study under C. S. Peirce and was one of the first women to receive a PhD from Johns Hopkins, she also, according to many modern commentators, solved a logical problem which had plagued the field of syllogisms since Aristotle. In this paper, we revisit this claim, posing and answering two distinct questions: Which logical problem did Ladd-Franklin solve in her thesis, and (...) which problem did she think she solved? We show that in neither case is the answer “a long-standing problem due to Aristotle.” Instead, what Ladd-Franklin solved was a problem due to Jevons that was first articulated in the nineteenth century. (shrink)

In 1883, while a student of C. S. Peirce at Johns Hopkins University, Christine Ladd-Franklin published a paper titled On the Algebra of Logic, in which she develops an elegant and powerful test for the validity of syllogisms that constitutes the most significant advance in syllogistic logic in two thousand years. Sadly, her work has been all but forgotten by logicians and historians of logic. Ladd-Franklin's achievement has been overlooked, partly because it has been overshadowed by the work of other (...) logicians of the nineteenth century renaissance in logic, but probably also because she was a woman. Though neglected, the significance of her contribution to the field of symbolic logic has not been diminished by subsequent achievements of others.In this paper, I bring to light the important work of Ladd-Franklin so that she is justly credited with having solved a problem over two millennia old. First, I give a brief survey of the history of syllogistic logic. In the second section, I discuss the logical systems called “algebras of logic”. I then outline Ladd-Franklin's algebra of logic, discussing how it differs from others, and explain her test for the validity of the syllogism, both in her symbolic language and the more familiar language of modern logic. Finally I present a rigorous proof of her theorem. Ladd-Franklin developed her algebra of logic before the methods necessary for a rigorous proof were available to her. Thus, I do now what she could not have done then. (shrink)

Before the early 1990s, accounts of classical American philosophy paid relatively little attention to the work and intellectual contributions of women philosophers. However, as early as 1991, a number of contemporary feminist philosophers and historians began to devote more focused attention to women philosophers whose intellectual achievements had been marginalized or forgotten. One woman philosopher whose contributions have still gone unnoticed is that of American logician, mathematician, and color theorist Christine Ladd-Franklin. This paper argues that Ladd-Franklin's feminist efforts to increase (...) the opportunities for women in professional academia were influenced not only by her work as a woman scientist and her reading of feminist literature but also by her understanding of pragmatism and her interaction with Charles Peirce. Specifically, Ladd-Franklin's arguments to increase academic research positions for women and her criticisms of male-only scientific societies point out how discrimination on the basis of gender violates Peirce's first rule of reason that one ought not block the road to inquiry and expose the unscientific nature of gender discrimination by contrasting the pragmatic meaning of acquiring a doctorate with the institutional practice of barring women from making intellectual contributions by denying them professorial positions. (shrink)