The veil of lākayfiyyat (absence of modality) had descended. The sciences that conveyed news of ittihād (union) and waḥdat al-wujūd (the oneness of being) began to cease and disappear. In this station that had been opened and written, iḥāṭa (encompassing everything), sarayān (effusion, flow), qurb (nearness), and maʿiyyat al-Dhāt (togetherness with the Divine Essence) became veiled. Then, as in the aforementioned relations concerning waḥdat al-wujūd, the certainty that the Exalted One (Hazret-i Sānī) is not established together with the world became known through yaqīn (certainty) attained by the path of yaqīn. On the contrary, as accepted in the view of the people of ḥaqīqa (inner reality)—may Allah reward their efforts—their understanding is that His iḥāṭa and qurb are only in the aspect of knowledge. He is not united with any of the things. He is Allah, and the world is the world. He is exalted above every modality and keyfiyyat (how-ness). The world, on the other hand, is arranged according to the order of keyfiyyat, from differentiation (varied creation) to pre-eternity (before creation). Therefore, it is not correct to assert that the world is free from keyfiyyat, that the one who arranges the order of keyfiyyat is the same as keyfiyyat itself, that the Necessary Being (al-Wājib) is identical to the possible existents (mumkināt), or that the Eternal (al-Qadīm) is the same as the originated (ḥādith).
Nonexistence (ʿadam) does not at all remove the essential possibility of the possible. It is also impossible, both rationally and according to the sacred law, for realities to undergo change. There is no correctness in transferring one to the other in any respect, for this is impossible in every way. What Shaykh Muhyiddin and his followers have said about the Necessary Essence (al-Wājib Dhāt) is astonishing. The Essence is not subject to any ruling; it is unknown and absolute (muṭlaq) existence.
Nevertheless, they have affirmed iḥāṭa, qurb, and maʿiyyat al-Dhāt. This ruling, for the Essence, is nothing but a ruling that exalts and declares Him transcendent. The correct view in this matter is the qurb and nearness of knowledge as stated by the scholars.
The emergence of sciences and maʿrifa (experiential knowledge of God) contrary to waḥdat al-wujūd caused me great distress. I thought that there was nothing higher than this tawhid (the oneness of God)—waḥdat al-wujūd, waḥdat al-shuhūd (1161). For this reason, I would supplicate to the Exalted Allah, humbly and with a broken heart, that He not grant me this maʿrifa, that is, the maʿrifa of tawhid al-wujūd, and that the veil over my state be completely lifted.
Then, the reality in the state and the clarity in the intention became manifest as required by the station, and the following became known: Although the world is the locus of manifestation for the perfections of the attributes and the appearance of the names, as advanced by the people of tawhid al-wujūd, the manifest locus (the thing manifested) is not identical to the manifesting one, nor is the shadow identical to the original. (Maktūbāt, I, 42)
Know that for the members of this Ṭarīqat-i ʿĀliyya (the exalted Sufi path), the tawhid that becomes manifest during the spiritual journey (sulūk) is divided into two: tawhid al-shuhūd and tawhid al-wujūd.
Tawhid al-shuhūd is the witnessing of the One (al-Wāḥid), that is, the realization by the sālik (spiritual traveler) that the existence he witnesses is nothing other than the One. Tawhid al-wujūd, on the other hand, is for the sālik to know and believe that existence is one, and to believe that all existents other than Him are nonexistent and to consider them as such. While believing that nothing exists besides Him, one also believes that these are loci of manifestation and places of appearance for this One. Tawhid al-wujūd is of the degree of ʿilm al-yaqīn (certainty through knowledge), while tawhid al-shuhūd is of the degree of ʿayn al-yaqīn (certainty through direct vision). This tawhid is one of the essential (ḍarūrī) principles of this tariqa. Thus, the state of fanāʾ (annihilation in God) cannot be realized without tawhid al-shuhūd, and ʿayn al-yaqīn cannot be attained without tawhid al-shuhūd. The witnessing of aḥadiyya (absolute oneness) in its entirety requires seeing nothing but Him. Tawhid al-wujūd, however, is not like this; it is not essential. ʿIlm al-yaqīn can be attained even without this maʿrifa. For ʿilm al-yaqīn, in its initial aim, does not require the negation of everything other than Him. This state is necessary only when the knowledge of the One through domination prevails and the negation of everything other than Him is required. (Maktūbāt, I, 56)
The first to clearly articulate tawhid al-wujūd was Muhyiddin Ibn ʿArabī. Even if the expressions of earlier shaykhs, while describing tawhid and ittihād (union), may be interpreted as referring to tawhid al-shuhūd. Since nothing other than the Real (al-Ḥaqq) was seen, some (as part of ecstatic utterances) said, "Mā fī jubbatī siwā Allāh" (There is nothing in my cloak but Allah), and some said, "Subḥānī mā..."