Adjoint Functors (& an Example in Logic)

http://photos4.meetupstatic.com/photos/event/6/2/5/4/event_88285172.jpeg'Adjoint functors' are a significant contribution that category theory makes to modern mathematics. Dean Casalena provides a concise summary of adjoint functors, coupled with an interesting illustration, that is available online (www.deancasalena.com/math/adjoint_functors.pdf). This paper is reasonably accessible and, thus, may serve as an interesting topic for meetup discussion.