The Communist Party of the Soviet Union (CPSU), formerly the Bolshevik Party, was a form of Bolshevism called Marxism–Leninism, an ideology of a centralised command economy with a vanguardist one-party state to realize the dictatorship of the proletariat. The Soviet Union's ideological commitment to achieving Marxist Communism included the National Communist development of socialism in one country and peaceful coexistence with capitalist countries while engaging in anti-imperialism to defend the international proletariat, combat the predominant prevailing global system of capitalism and promote the goals of Russian Communism. The state ideology of the Soviet Union—and thus Marxism–Leninism—derived and developed from the theories, policies and political praxis of Marx, Lenin and Stalin. Marxism–Leninism Marxism–Leninism was the ideological basis for the Soviet Union. It explained and legitimized the CPSU's right to rule, while explaining its role as a vanguard party. For instance, the ideology explained that the CPSU's policies, even if they were unpopular, were correct because the party was enlightened. It was represented to be the only truth in Soviet society, and with it rejecting the notion of multiple truths. In short, it was used to justify CPSU Leninism as being a means to an end. The relationship between ideology and decision-making was at best ambivalent, with most policy decisions taken in the light of the continued, permanent development of Marxism–Leninism, which, as the only truth, could not by its very nature become outdated. Despite having evolved over the years, Marxism–Leninism had several central tenets. The main tenet was the party's status as sole ruling party. The 1977 Constitution referred to the party as the "leading and guiding force of Soviet society, and the nucleus of its political system, of all state and public organizations, is the Communist Party of the Soviet Union.