sentences:  More recently, the South African Communist Party and Socialist Alliance have re-elaborated the two-stage theory, although the Socialist Alliance differentiates their position from the Stalinist one.The two-stage theory is often attributed to Karl Marx and Friedrich Engels, but critics such as David McLellan and others dispute that they envisaged the strict application of this theory outside of the actually existing Western development of capitalism.Although all agree that Marx and Engels argue that Western capitalism provides the technological advances necessary for socialism and the "grave diggers" of the capitalist class in the form of the working class, critics of the two-stage theory, including most trends of Trotskyism, counter that Marx and Engels denied that they had laid down a formula to be applied to all countries in all circumstances.