Natural sciences are branches of knowledge which deal directly with the phenomena exhibited by natural objects, organic or inorganic, and their substances. There exists among such entities an inexorable regularity in the concatenation and sequence of natural events or physical phenomena. While measurements of such substances may not be precise, they are sufficiently so to permit the use of laboratory experiments and observation for measurements and quantification of knowledge. Sometimes referred to as the physical or empirical sciences, the natural sciences include biology, geology, medicine, physics, chemistry, etc., but not the human sciences, mathematics, philosophy or metaphysics.
- Percy L. Greaves, Jr. "Mises Made Easier ", 1974. Referenced 2014-08-17.