Scientific Method: Parsimonious - sparing in proposed explanations - Occam's Razor

One of the requirements of the Scientific Theory / Scientific Method is Parsimonious: sparing in proposed entities or explanations, see Occam's Razor

Occam's razor (also spelled Ockham's razor) is a principle attributed to the 14th-century English logician and Franciscan friar William of Ockham (Guilhelmi Ockam and Guillermi de Ockam in Latin [1]). Originally a tenet of the reductionist philosophy of nominalism, it is more often taken today as a heuristic maxim that advises economy, parsimony, or simplicity in scientific theories.

Occam's razor states that the explanation of any phenomenon should make as few assumptions as possible, eliminating, or "shaving off", those that make no difference in the observable predictions of the explanatory hypothesis or theory. In short, when given two equally valid explanations for a phenomenon, one should embrace the less complicated formulation. The principle is often expressed in Latin as the lex parsimoniae (law of succinctness):

entia non sunt multiplicanda praeter necessitatem,

which translates to:

entities should not be multiplied beyond necessity.

This is often paraphrased as "All things being equal, the simplest solution tends to be the best one." In other words, when multiple competing theories are equal in other respects, the principle recommends selecting the theory that introduces the fewest assumptions and postulates the fewest hypothetical entities. It is in this sense that Occam's razor is usually understood.

Karl Popper

Karl Popper argues that a preference for simple theories need not appeal to practical or aesthetic considerations. Our preference for simplicity may be justified by his falsifiability criterion: We prefer simpler theories to more complex ones "because their empirical content is greater; and because they are better testable" (Popper 1992). In other words, a simple theory applies to more cases than a more complex one, and is thus more easily refuted.

Science by Razor alone?

When it is proposed as a maxim of science, Occam's razor is construed as a decision procedure for choosing among competing systems of hypotheses. In this context a system of hypotheses, together with its supporting definitions and its logical consequences, is commonly described as a theory.

Occam's razor has become a basic tool for those who follow the scientific method. The primary activity of science — formulating theories and selecting the most promising ones — is impossible without a way of choosing from among the theories which fit the evidence equally well, the number of which can be arbitrarily large (see underdetermination).