The Islamic Doctrine is contained as a whole in the Tawhid, The "affirmation of Divine Unity". For the ordinary believer this affirmation is the clear and simple axis of the religion. For the contemplative it is the door, which opens on to essential reality. The further the mind of the contemplative penetrates into the apparent rational simplicity of the Divine Unity, the more complex that simplicity will become; the several aspects which the reason acknowledges as belonging to Unity will be more and more fully grasped till a point is reached where their contrasts can no longer be grasped by discursive thought alone. In other words it is only intuition beyond form that has access to Unity. The central concept in Ibn 'Arabi's system is wahdat-ul-wujud, "unity of being". Scholars have debated whether Ibn 'Arabi intends this term to describe a monist system, where nothing exists but the One. An affirmative response does not indicate, however, a dramatic shift in Muslim metaphysics because in reality, Ibn 'Arabi is only taking the Ash'ari synthesis to its logical extreme. The Ash'ari insistence on God's total omnipotence and control over the universe implies that God is the only true agent. It is not illogical, therefore, to suggest, as Ibn 'Arabi does, that God must also be the only true existent. In the Wisdom of The Prophets, Muhyi-d-Din ibn 'Arabi describes supreme Union as a mutual interpretation of Divinity and man. God as it were takes on human nature; the Divine nature (al-Lahut) becomes the content of human nature (an-Nasut), the latter being considered as the recipient of the former, and from another angle man is absorbed and as it were, enveloped by Divine Reality. God is mysteriously present in man and man is obliterated on God. All this has to be understood with a spiritual point of view related to spiritual realization. In setting side by side these two reciprocal modes of the interpretation of God and man ibn 'Arabi adds, in the chapter on Abraham, that "here are two aspects of one and the same state, which are neither merged together nor yet added one to the other." In the first mode God reveals Himself as the real Self, which knows through the faculties of perception of man and acts through his faculties of action. In the second and inverse mode, man moves, so to speak, in the dimensions of Divine Existence, which in relation to him is polarized so that to each human faculty or quality there corresponds a Divine aspect. This is expressed in the sacred utterance (hadith qudsi): "He who adores Me never ceases to approach Me until I love him, and when I love him I am the hearing by which he hears, the sight by which he sees, the hand with which he grasps and the foot with which he walks." In so far as it is united to the Divine Spirit, man's spirit knows all things principally since henceforward nothing is outside his own essence, but his essential and global knowledge only becomes differentiated in so far as the light of intellect falls on individual things. On the other hand the individual subject of Divine Man inevitably subsists in a certain manner; it no longer subsists in the sense that it is only in his identification with the Divine Intellect that this being, who still bears the name of 'man', really feels that he his 'himself'; nevertheless, if the individual subject did not subsist in any sense whatsoever, there would be no subjective continuity linking together his human experiences. In the man who is spiritually perfect the relationship between the Divine Reality (Haqiq'ah) and the still subsisting individuality is one of the most difficult things to grasp. For the man who has arrived at this perfection the Divine Reality is indeed no longer "veiled" by anything, whereas individual consciousness is by very definition a "veil" (Hijab) and exists only in as much as it refracts the blinding light of the Divine Intellect. Union with God is also conceived under the aspect of "assimilation of the Divine Qualities" (al-ittisaf bis-Sifat al-ilahiyyah), an assimilation which must be understood in a purely intellective sense as knowledge of the Divine Qualities or Presences (Hadarat). Again this "assimilation of the Divine Qualities" has its symbolic reflection in the soul in the form of the spiritual virtues and its model is nothing other than the "Universal Man". Over here it would be relevant to quote Reynold A. Nicholson who says "Since the 'humanity' (nasut) of God comprises the whole bodily and spiritual nature of man, the 'divinity' (lahut) of God cannot unite with that nature excepts by means of an incarnation or, to adopt the term infusion (hulul) of the Divine Spirit, such as takes place when the human spirit enters the body."