These sentences appear in the August, 1980, issue of the Socialist Standard, official journal of the SPGB:
(Rosa Luxemburg) therefore tried to show where Marx had gone wrong, but only succeeded in exposing her own utter confusion about economics. She made the silly mistake of assuming that the level of Market demand was determined exclusively by consumption.
If Rosa Luxemburg, holder of a degree in economics, a person who had positive ideas regarding Marxism and was prepared to study it, is liable to get utterly confused about economics and to make a “silly mistake,” then how can the worker be expected to arrive at ideas about economics which preclude confusion about the subject and refrain from making what the Socialist Standard regards as silly mistakes?
It is sometimes argued by the SPGB that “socialist understanding does not require a thorough knowledge of Marxism. However, the article in question is not one about theory, is a polemic against another sect which holds “that capitalism is and has been since the first world war, in a state of economic collapse due to its inability to find new markets on which to sell its products at a profit” and that “this view is based on an uncritical acceptance of the analysis Made by Rosa Luxemburg in her book The Accumulation of Capital. According to the Socialist Standard her argument was based on a “simple fallacy.” In other words, a knowledge of economic theory, which to the SPGB includes Marxist economics, is necessary, to counter the arguments of a rival sect.
from Ideological Commentary 8, November 1980.