Reform versus revolution

Disagreements concerning social reform and social revolution have divided radical leftists, including Marxists, since the birth of modern leftism during the French Revolution. Revolutionaries or revolutionists support a forcible overthrow of the current political and economic system, whereas reformists believe that radical change within the current system is possible and desirable, holding revolution to be immoral, counterproductive, or unrealistic. Reformists and revolutionists tend to differ on other issues as well: for instance, few reformists believe that their support of social reforms is likely to bring about a communist society, whereas revolutionists are likely to view a communist society as non-negotiable.

Karl Marx advocated for violent revolution for most of his life, and many Marxists therefore hold reformism to be revisionist: Eduard Bernstein, for instance, was castigated by Lenin and Rosa Luxemburg for his reformist ideas. Most academic Marxists (such as "Marxian" economists), on the other hand, are unsurprisingly reformists who do not advocate for or theorize about a classless or wageless society.

Many leftist tendencies and ideas have become reformist as their class base has shifted towards the middle class, educated professionals, or the petit bourgeoisie. Thus social democracy, originally a term for radical socialism, came to refer to a new, reformist political theory after such a shift occurred in postwar Europe, and social democratic parties are now considered neoliberal by even modestly heterodox economists.

The distinction between reform and revolution should not be confused for a strict separation. Many strains of thought, including Marxism and some forms of anarchism, advocate reform as a legitimate or even necessary element of revolutionary politics. Karl Marx made it clear that his theory included the necessity of reforms which strengthened the position and consciousness of the working class movement. In 1880, upon learning that Jules Guesde and other self-proclaimed Marxists only supported reformist demands with the hope that they would be utterly resisted by the capitalist state and thereby drive the working class towards radicalism, Marx insisted that "I myself am not a Marxist". The position criticized by Marx is known today as impossibilism and is related to the theory and practice of anarcho-syndicalist groups like the Industrial Workers of the World.