Thesis: Ph. D., Massachusetts Institute of Technology, Department of Linguistics and Philosophy, 2016.Cataloged from PDF version of thesis.Includes bibliographical references.An investigation of the imagination, as both a mental process and a capacity to acquire knowledge about the world and other minds. It is argued that imagination is a unique mental process, whose primary feature is the capacity to construct and manipulate sets of mental representations. This feature unifies the diverse activities we call imaginings into a single class. In addition, use of this capacity in a rule-based way, under the constraint of prior beliefs, can help us acquire knowledge of everyday facts. An examination is then made into the limitations of such a ca...