Ideology permeates these states. According to scholar Peter Tang, "he supreme test of whether a Communist Party-state remains revolutionarily dedicated or degenerates into a revisionist or counterrevolutionary system lies in its attitude toward the Communist ideology." Therefore, the sole ideological purpose of communist states is to spread socialism and to reach that goal these states have to be guided by Marxism–Leninism. The communist states have opted for two ways to achieve this goal, namely govern indirectly by Marxism–Leninism through the party (Soviet model), or commit the state officially through the constitution to Marxism–Leninism (Maoist China–Albania model). The Soviet model is the most common and is currently in use in China.