"Fields of study are often distinguished in terms of hard sciences and soft sciences and these terms (at times considered derogatory) are often synonymous with the terms natural and social science (respectively). Physics, chemistry, biology and geology are all forms of "hard sciences". Studies of anthropology, history, psychology, and sociology are sometimes called "soft sciences." Even within the fields there is sorting of the fields. Although it might be difficult to say whether geology or biology is "harder", physics is usually considered the "hardest". Especially "hard" are the fields of high energy physics and cosmology. In this usage, "hard" means mathematic, or in experimental area, expensive.
Proponents of this division use the arguments that the "soft sciences" do not use the scientific method, admit anecdotal evidence, or are not mathematical, all adding up to a "lack of rigor" in their methods. Opponents of the division in the sciences counter that the "social sciences" often make systematic statistical studies in strictly controlled environments, or that these conditions are not adhered to by the natural sciences either (for example, behavioral biology relies upon fieldwork in uncontrolled environments, astronomy cannot design experiments, only observe limited conditions). Opponents of the division also point out that each of the current "hard sciences" suffered a similar "lack of rigor" in its own infancy." (Wikipedia, 2005).