Occam's razor states: other things being equal—when several theories explain the same facts equally well, it is rational to prefer the most parsimonious of the theories. Occam's razor, sometimes referred to as "ontological parsimony", commonly is attributed to William of Ockham in the 14th-century, although it probably predates him.
We are not allowed to affirm a statement to be true or to maintain that a certain thing exists, unless we are forced to do so either by its self-evidence or by revelation or by experience or by a logical deduction from either a revealed truth or a proposition verified by observation.
- Baker, Alan (February 25, 2010). Edward N. Zalta (ed.):Simplicity; §2: Ontological parsimony. The Stanford Encyclopedia of Philosophy (Summer 2011 Edition). Retrieved on 2011-11-14.
- William of Ockham (1990). “Introduction §4”, Philotheus Boehner (translator): Ockham - Philosophical Writings: A Selection, Latin works and English translation. Hackett Pub Co, p. xx. ISBN 0872200787.
- Richard Olson (1983). “Theology and natural science in the medieval university; The condemnations of 1277: Scientific and theological consequences”, Science Deified and Science Defied: The Historical Significance of Science in Western Culture, Vol. 1: From Bronze Age to the Beginnings of the Modern Era, Ca 3500 B.C. to A.D. 1640. University of California Press, p. 200. ISBN 0520047168. This quotation plus a discussion of William of Ockham's role in his time.