That part of Euclidean geometry that deletes any reference to parallel lines or notions directly provable from them is known as absolute geometry. Although perhaps puzzling, there is a perfectly logical reason for this term. One of the early pioneers in geometry, János Bolyai (1802-1860), set out to discover what must be true about three-dimensional space without introducing the concept of parallelism. Any logical consequence thereof would then be an absolute truth about the universe, thus the term.