This research tries to analyze necessities of left party’s thoughts in terms of time and place during initial two decades after the revolution applying Dilthey’s historicism. This method as a school of sociology of knowledge, believes that thoughts are derived from conditions of time and place in the society. Findings of this research indicate that left party’s viewpoints and stances during 80s are totally different from its viewpoints and stances during 90s. Influenced by internal and international environment, supporters of left party have moved from their stances of supporting governmental economy, negating manifestations of western culture and anti-imperialistic inclinations during the first decade to their stances of supporting free economy, civil society and principle of détente in foreign policy during the second decade.