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 often differ on other issues: for instance, few reformists argue that a communist society is likely to arise through social reform, and revolutionists often consider reformist proposals like mixed economies unacceptable.

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.