How did Marx's scientific brand of socialism differ from utopian or practical socialists?

Scientific socialism is based on an analysis of existing material (economic and technological) conditions of society and of their development, and uses this analysis to predict probable future outcomes in terms of where society is moving toward. Socialism was seen as a logical outcome of capitalist development and capitalist crises in Marxist theory.

In contrast, Utopian socialists start from an ideal vision of society, which is based on subjective value-judgements, and then try to move society in that direction. Marx would argue that the idea of "utopianism" is naive, because one person's utopia might be another person's Dystopia and vice versa.

Practical socialists, such as social democratic reformers, do not base their arguments on any comprehensive theory. They are based on populism and attempting to help as many people through immediate, existing means by calling for popular reforms, social programs and regulations to benefit the lives of ordinary people. Most popular socialists disregard or are not even sure what socialism is because they are consumed with these popular, practical reforms within capitalism.