Many branches of philosophy are relevant to an understanding of geographic information, especially metaphysics and epistemology. Philosophical theories are deeply engaged in the study of knowledge, space, time, geographic phenomena and human interaction with them. These theories influence the development of geographic ontologies and the structuring, analysis, and interpretation of geographic information. It is, therefore, crucial for professionals to understand these principles in order to bridge (rather than eliminate) the differences and work together. Philosophical perspectives on GIS practice are covered in Unit GS7 Critical GIS.