Mary Leng is a lecturer in philosophy at the University of Liverpool. Her research focus is the philosophy of mathematics, and she has been particularly concerned with the nature of mathematical knowledge. She is currently working on the issue of ontological commitment to mathematical objects and on the applicability of mathematics in natural science. Educated at Balliol College, Oxford, where she took her baccalaureate degree with honors, she earned a Ph.D. in philosophy from the University of Toronto in 2001. Dr. Leng has been a visiting fellow in the Department of Logic and the Philosophy of Science at the University of California at Irvine, and after a postdoctoral fellowship in the humanities at the University of Toronto, she held a research fellowship at St. John’s College, Cambridge, for four years. She was appointed to her present position last autumn. Dr. Leng has been a visiting junior fellow at the Peter Wall Institute for Advanced Studies at the University of British Columbia. In addition to papers published in professional journals, she is the co-editor (with Alexander Paseau and Michael Potter) of Mathematical Knowledge, which will be published by Oxford University Press (OUP) later this year, and the author of Mathematics and Reality, which OUP will publish in 2008.