Question: How many books did Hadley Arkes's philosophy professor at the University of Chicago publish?
Context: Michael Levin ( ; born 21 May 1943) is a philosophy professor at City University of New York.  He has published on metaphysics, epistemology, race, homosexuality, animal rights, the philosophy of archaeology, the philosophy of logic, philosophy of language, and the philosophy of science. Arkes received a B.A. degree at the University of Illinois and a Ph.D. from the University of Chicago where he was a student of Leo Strauss. Warren A. Shibles was an American philosopher, historian and professor.  His B.A. is from the University of Connecticut and his M.A. from the University of Colorado.  He was head of the department of philosophy of the University of Wisconsin-Whitewater.  He is the author of numerous articles in history and philosophy and of many books, including children's books in philosophy and ethics.  A number of his books have been translated into German, Finnish and Spanish languages. Debra Nails (born November 15, 1950) is an American philosophy professor and well known classics scholar currently teaching at Michigan State University.  Nails earned her M.A. in philosophy and classical Greek from Louisiana State University before going on to earn a Ph.D. in philosophy at the University of the Witwatersrand, Johannesburg in 1993.  Previously, she taught in the Department of Classics, Philosophy, and Religion at Mary Washington College.  Nails currently teaches courses on the history of philosophy, continental rationalism, metaphysics, and modern philosophy. George E. Mattson is a well known author of martial arts books and one of the first Americans to be awarded a black belt in Uechi-ryū Karate-do.  He was the first to teach the style professionally resulting in the majority of the original growth in the United States of America.  He was one of the very first to publish a book in English about karate and has since continued to publish many books on Uechi-Ryu. C. D. C. Reeve (born September 10, 1948) is a philosophy professor at the University of North Carolina at Chapel Hill.  He works primarily in Ancient Greek philosophy, especially Plato and Aristotle.  He is also interested in philosophy generally, and has published work in the philosophy of sex and love, and on film.  He has also translated many Ancient Greek texts, mostly by Plato. Leo Strauss ( ; ] ; September 20, 1899 – October 18, 1973) was a German-American political philosopher and classicist who specialized in classical political philosophy.  He was born in Germany to Jewish parents and later emigrated from Germany to the United States.  He spent most of his career as a professor of political science at the University of Chicago, where he taught several generations of students and published fifteen books. Werner Erhard: The Transformation of a Man, The Founding of est is a biography of Werner Erhard by philosophy professor William Warren Bartley, III.  The book was published in 1978 by Clarkson Potter.  Bartley was professor of philosophy at California State University and had studied with philosopher Karl Popper.  He was the author of several books on philosophy, including a biography about Ludwig Wittgenstein.  Prior to writing the book, Bartley was a friend of Erhard's and was involved in his company Erhard Seminars Training ("est").  While writing the book, Bartley was paid US$30,000 in the role of philosophical consultant for est.  Erhard wrote a foreword to the book.  The book's structure describes Erhard's education, transformation, reconnection with his family, and the theories of the est training. David Farrell Krell (born 1944), is Professor Emeritus of philosophy at DePaul University.  He received his Ph.D. in philosophy at Duquesne University, where he wrote his dissertation on Heidegger and Nietzsche.  He has taught at many universities in Germany, France, and England.  Specializing in Continental Philosophy, he has written many books on Heidegger and Nietzsche, including "Daimon Life: Heidegger and Life Philosophy" (1992), "Intimations of Mortality: Time, Truth, and Finitude in Heidegger's Thinking of Being" (1986), "The Good European: Nietzsche's Work Sites in Word and Image" (1997), and "Infectious Nietzsche" (1996).  Additionally, Krell has written extensively about German Idealism, his books in this area include "The Tragic Absolute: German Idealism and the Languishing of God" (2005), and "Contagion: Sexuality, Disease, and Death in German Idealism and Romanticism" (Indiana, 1998).  Krell has also translated Heidegger's lectures on Nietzsche, and was the editor of Heidegger's "Basic Writings" (1977).  In a 2005 interview, Krell cited Jacques Derrida as a major influence on his work on Nietzsche. Dario Antiseri (born 1940 in Foligno) is a Philosophy professor.  He holds a bachelor's degree (summa cum laude) in Philosophy from the University of Perugia and for many years he has been Full Professor of Methodology of the Social Sciences at LUISS, in Rome.  He taught in Siena, Padova and Rome, where he was also the Dean of the Faculty of Political Science.  He retired from academia in 2010.  He is an important scholar of Karl R. Popper and Hans-Georg Gadamer, and in many works he tries to show the links between fallibilism and hermeneutics.  In 1996 he published a book about Gianni Vattimo's "weak thought".  With the Italian philosopher Giovanni Reale he is also author of an important treatise of philosophy in three volumes, which is the most widely used philosophy textbook in Italian schools.
Answer: fifteen