Left-unity
Left-unity is a slogan which calls for the unification of various left-wing political movements. Left-unity diverges in its aims, ranging from calls for limited, tactical unity between leftists in practical activities to unprincipled and opportunist stances which deny the need for splits with revisionist tendencies (e.g. between Leninism and Trotskyism, Leninism and Kautskyism, etc.).
Forms
Marxist unity
Marxist unity is a slogan circulated by nascent Marxists and outright opportunists. Many advocates of "Marxist unity" claim that because the historical splits in the communist movement took place many decades ago, they no longer hold relevance to the world proletariat. This slogan is ignorant in elementary communist history. For instance, the split between Leninists and Trotskyites took place out of fundamental disagreements with regard to party building and the role of the peasantry in building socialism. Trotskyites undermine democratic centralism and seek to build factions within the party while adopting a deeply hostile outlook towards the peasants, making them the natural enemies of communists in the imperialized countries.
Anarchist unity
Anarchist unity is the notion that the various petite-bourgeois anarchist tendencies such as anarcho-communism or anarcho-syndicalism can merge into a single political movement. This movement is often known as "anarchism without adjectives". Contrary to the unworkable "Marxist unity", anarchists are generally united in their utopianism, hatred of communism, and petite-bourgeois insurrectionism.