"The seat of knowledge in man is a spiritual substance which is variously referred to in the Holy Qur'an sometimes as his heart (al-qalb), or his soul or self (al-nafs), or his spirit (al-ruh), or his intellect (al-'aql). In virtue of the truth that man knows God in His absolute unity as his Lord, such knowledge, and the reality of the situation that necessarily follows from it, has bound man in a covenant (al-mithaq; al-'ahd) determining his purpose and attitude and action with respect to his self in his relation to God.
This binding and determining of man to a covenant with God and to a precise nature in regard to his purpose, attitude, and action, is the binding and determining in religion (al-din) which entails true submission (al-islam). Thus knowledge and religion are natural correlates in the nature of man, that is, the original nature in which God has created him (al-fitrah). Man's purpose is therefore to know and to serve God ('ibadah) and his duty is obedience (ta'ah) to God, which conforms with his essential nature created for him by God.
But man is also "composed of forgetfulness (nisyan)" - as a Prophetic tradition says, and he is called insan basically precisely because, having testified to himself the truth of the covenant he sealed with God, which entails obedience of His commands and prohibitions, he forgot (nasiya) to fulfill his duty and purpose. Hence according to ibn 'Abbas with reference to a passage in the Holy Qur'an, the term insan is derived from nasiya when he said that man is called insan because, having covenanted with God, he forgot (nasiya).
Forgetfulness is the cause of man's disobedience, and this blameworthy nature inclines him towards injustice (zulm) and ignorance (jahl). But God has equipped him with the powers and faculties of right vision and apprehension, of real savouring of truth, of right speech and communication; and He has indicated to him the right and the wrong with respect to the course of action he should take so that he might strive to attain his bright destiny. The choice for the better (ikhtiyar) is left to him.
Moreover, God has equipped him with intelligence to know and distinguish reality from non-reality, truth from falsehood, and rectitude from error; and even though his intelligence - or rather his imaginative and estimative faculties - might confuse him, and provided he is sincere and true to his noble nature, God, out of His bounty, mercy, and grace, will aid and guide him to attain to truth and right conduct. The supreme example of this is the case of the Prophet Ibrahim, upon him be peace.
Man thus equipped and fortified is meant to be the vicegerent (khalifah) of God on earth, and as such the weighty burden of trust (amanah) is placed upon him - the trust and responsibility to rule according to God's will and purpose and His pleasure. The trust implies responsibility to rule with justice, and the 'rule' means not simply ruling in the socio-political sense, nor in the controlling of nature in the scientific sense, but more fundamentally in its encompassing of the meaning of nature (al-tabi'ah), it means the ruling, governing, controlling, and maintaining of man by his self or his rational soul."
(p 143-145 of "Prolegomena to the Metaphysics of Islam" by Sayyid Naquib al-Attas)