Books in Hannon Library are arranged by topic, according to the Library of Congress Classification System. If you want to browse the physical collection, look for these call number ranges on the 2nd Floor of the library, but note that 2/3 of the library's collection is housed in Basement Storage.
B 1 - 5802 Philosophy - General (also individual philosophers and schools, time periods, regions, religions)
BC 1 - 199 Logic
BD 10 - 701 Speculative philosophy (metaphysics, epistemology, ontology, cosmology)
BJ 1 - 2195 Ethics
More books pertaining to philosophy are in the Reference Section (Information Commons) and Basement Storage (request through the library catalog). Some may be in other call number ranges.