The Primary Obligation of Man, Self-Knowledge or Theology

Muslim theologians generally believe that the first duty of a man is reflecting on God. Ash'ari theologians think that this duty has been tradition and driven from Qur'anic verses and hadiths and Ijma' (consensus), but in Mu'tazilites theologians' view, this duty is based on reason and they adduced two arguments in this regard; first, “probable harm” and second, “necessity gratitude to the Blessing Giver”. This paper claims that arguments of both parties are incomplete, and the first duty of man, is "self knowledge" not" knowing God or theology ". It is a rational duty because that is reasonable to achieve perfection and prosperity, self-Knowledge is essential, of course, in self-knowledge; in next steps knowing other fundamental issues come in turn. It is known that theologian is claimer and if he fails to prove its claim, the claim of atheist will necessarily be proved but according to the second argument all human are accounted a claimer and every party has to represent its explanation regarding its claim and incapability of one party in proving its claim would not mean that other party's claim to be proven.