http://en.wikipedia.org/wiki/Occam's_razor
"Occam's razor (also written as Ockham's razor, Latin lex parsimoniae) is the law of parsimony, economy or succinctness. It is a principle urging one to select from among competing hypotheses that which makes the fewest assumptions.
...
The razor asserts that one should proceed to simpler theories until simplicity can be traded for greater explanatory power."