“There comes a time in the life of a young Mathematician when he must put down his pencil and think about the future.” This is how John “Jack” R. Quine begins a letter to his “Dear Cousin Van,” better known as W. V. Quine, a renowned philosopher and Harvard professor (**MS Am 2587 [891], 008937558, above**). Jack, who declares that “Abstract mathematics is not for me,” likes math “with some content: physical, philosophical, or even historical.” This is what lies at the core of the Applied Mathematics concentration at Harvard: a desire to use the science of numbers—also encompassing statistics and computer science—to solve “the not so clear cut problems” of the real world.

Quine’s papers are a treasure trove of material connected to Applied Math. They hold, for example, Quine’s correspondence with Swiss psychologist Jean Piaget (**852**), which includes some essays connecting mathematics and developmental psychology. Students can also find letters between Quine and Hilary Putnam (**885**), in which the philosopher and the mathematician discuss papers and ideas relating their two subjects, as well as personal matters. Concentrators exploring the Quine archive also have access to collected papers by other scholars, which can also be a source of material connected to Applied Math. These include John A. Paulos’ “Probabilistic, Truth-Value, and Standard Semantics and the Primacy of Predicate Logic” (**2067**), which joins concepts from mathematics, linguistics, and philosophy, and Alvin Plantinga’s “Transworld Identification, United Airlines, and Quine’s Objection to Quantified Modal Logic” (**2089**), another partnership between philosophy and mathematical logic.

Besides the Quine papers, Houghton has multiple other volumes—some illustrious and some less known—that Applied Math concentrators can use in their research efforts. They include an Alexander Graham Bell pamphlet, originally intended for private circulation, titled “Upon the Electrical Experiments to Determine the Location of the Bullet in the Body of the Late President Garfield” (**Phys 3506.1*, 004170953**), which can be studied in conjunction with Electrical Engineering and Engineering Sciences. The library also holds a first edition copy of Galileo Galilei’s *Sidereus Nuncius*, which can be jointly assessed with Astrophysics. Houghton also has a wealth of items on economics that can be analyzed from an Applied Math perspective. A series of broadsides containing many documents from the interwar period (**Econ 13.5**), for example, contains “The Economic Position of Europe in Comparison with the U.S.” (**005421503**), which can be used from an economic and a historical perspective. Two older treatises in the collection connect mathematics to more unorthodox subjects. One of them, *Mathematical Psychics* (**Econ 674.1*, 002199837**), studies the “moral sciences” from a mathematical perspective, while the other, *Théorie Mathématique de la Richesse Sociale* (**Econ 463.1.20*, 006862031**), can be used to explore problems also studied by disciplines such as Sociology.