Scientific socialism is the term first used by Friedrich Engels to describe the social-political-economic theory first pioneered by Karl Marx. The purported reason why this form of socialism is "scientific socialism" (as opposed to "utopian socialism") is that it is said to be based on the scientific method, in that its theories are held to an empirical standard, observations are essential to its development, and these can result in changes and/or falsification of elements of the theory.