Everyone should read this new entry in the SEP.
Emily Elizabeth Constance Jones (1848–1922), a contemporary of Bertrand Russell and G. E. Moore at Cambridge University, worked primarily in philosophical logic and ethics. Her most significant contribution to the former area is her application of the intension-extension distinction to singular terms, anticipating Frege's related distinction between sense and reference and Russell's pre-“On Denoting” distinction between meaning and denotation. Widely regarded as an authority on philosophical logic by figures as diverse as F. C. S. Schiller and G. F. Stout on the one hand and C. S. Pierce on the other … Russell delivered a paper to the Moral Sciences Club, subsequently published as “Knowledge by Acquaintance and Knowledge by Description”, responding to a critical paper by Jones, delivered to the same society some months earlier. Jones also published in ethics, and was regarded by Henry Sidgwick, her mentor, as one of his prize students. Yet, despite the fact that she published numerous articles, a monograph and several textbooks (some going into multiple editions), and was a very visible member of the English philosophical community from the 1890s until her death in 1922, she is now almost entirely forgotten.
Next time I'm teaching history of analytic philosophy, I'll assign Jones (and Stebbing). Not sure why I didn't do it this year: I did assign Russell's "Knowledge by acquaintance" after all!
Jones was not the only woman contributing to philosophical logic and related areas at the beginning of the twentieth century: Pierce's student, Christine Ladd-Franklin (1847-1930) made significant contributions to logic and psychology, and the writings of Lady Victoria Welby (1837–1912) on meaning were widely read. … Later figures include the philosopher of science, Dorothy Wrinch (1894–1976), a Girton student who went on to study under Russell, and Susanne Langer (1895–1985), who wrote a dissertation under Alfred North Whitehead at Radcliff in 1926. Wrinch, who published papers in Mind on, among other things, the theory of relativity, later abandoned philosophy for chemistry, teaching for many years at Smith College. Langer, who later achieved prominence in the philosophy of art, published several technical articles on type theory and related topics early in her career (see, for example, Langer 1926, 1927). Possibly the most prominent woman analytic philosopher of the first half of the twentieth century, however, was another Girton student, L. Susan Stebbing (1885–1943), Professor of Philosophy at Bedford College, London, and co-founder of the journal Analysis.