Scientific socialism is a term coined in 1840 by Pierre-Joseph Proudhon in his What is Property? to mean a society ruled by a scientific government, i.e. one whose sovereignty rests upon reason, rather than sheer will:
Thus, in a given society, the authority of man over man is inversely proportional to the stage of intellectual development which that society has reached; and the probable duration of that authority can be calculated from the more or less general desire for a true government, -- that is, for a scientific government. And just as the right of force and the right of artifice retreat before the steady advance of justice, and must finally be extinguished in equality, so the sovereignty of the will yields to the sovereignty of the reason, and must at last be lost in scientific socialism.
Although the term socialism has come to mean specifically a combination of political and economic science, it is also applicable to a broader area of science encompassing what is now considered sociology and the humanities. The distinction between Utopian and scientific socialism originated with Marx, who criticized the Utopian characteristics of French socialism and English and Scottish political economy. Engels later argued that Utopian socialists failed to recognize why it was that socialism arose in the historical context that it did, that it arose as a response to new social contradictions of a new mode of production, i.e. capitalism. In recognizing the nature of socialism as the resolution of this contradiction and applying a thorough scientific understanding of capitalism, Engels asserted that socialism had broken free from a primitive state and become a science. This shift in socialism was seen as complementary to shifts in contemporary biology sparked by Charles Darwin and the understanding of evolution by natural selection--Marx and Engels saw this new understanding of biology as essential to the new understanding of socialism and vice versa.
Similar methods for analyzing social and economic trends and involving socialism as a product of socioeconomic evolution have also been used by non-Marxist theoreticians, such as Joseph Schumpeter and Thorstein Veblen.
Scientific socialism refers to a method for understanding and predicting social, economic and material phenomena by examining their historical trends through the use of the scientific method in order to derive probable outcomes and probable future developments. It is in contrast to what later socialists referred to as Utopian socialism--a method based on establishing seemingly rational propositions for organizing society and convincing others of their rationality and/or desirability. It also contrasts with classical liberal notions of natural law, which are grounded in metaphysical notions of morality rather than a dynamic materialist or physicalist conception of the world.
Scientific socialists view social and political developments as being largely determined by economic conditions as opposed to ideas in contrast to Utopian socialists and classical liberals and thus believe that social relations and notions of morality are context-based relative to their specific stage of economic development. Therefore, as economic systems both socialism and capitalism are not social constructs that can be established at any time based on the subjective will and desires of the population, but instead are products of social evolution. An example of this was the advent of agriculture which enabled human communities to produce a surplus--this change in material and economic development led to a change in social relations and rendered the old form of social organization based on subsistence-living obsolete and a hindrance to further material progress. Changing economic conditions necessitated a change in social organization.
In his book The Open Society and Its Enemies, the philosopher of science Karl Popper characterized scientific socialism as a pseudoscience. He argues that its method is what he calls "historicism", i.e. the method of analyzing historical trends and deriving universal laws from them. He criticizes this approach as unscientific as its claims cannot be tested and in particular are not subject to being disproven.