In existographies, Al-Tawhidi (923-c.1015) (IQ:#|#) (LH:3) (EPD:MF) was a Persian philosopher, characterized a top three zindiq of Islam, along with al-Rawandi and al-Marri (Warraq, 1995), noted for 
In 971, Tawhidi, in Baghdad, studied Aristotelian philosophy under Yahya ibn Adi.
His collected works total 5,000 printed pages.
His work, according to Margoliouth (1905), was considered “more dangerous” than al-Rawandi or al-Marri, because, whereas these two proclaimed their unbelief openly, al-Tawhidi expressed his unbelief in innuendoes. Said to have disdain for theological disputation.
His reputation as an author after his death suffered from his double association with Mutazilism and Sufism , which often led conformist Muslims to accuse him of unbelief (kufr), heresy (zandaqa), and atheism (ta 'ṭil). His positions have been qualified as "philosophico-mystical", attracted as he was both by Sufism and by the Neoplatonizing Aristotelianism of the circle of al-Sijistani, and sharing the latter's ideas (against the mutazilites) on the separation between philosophy and religion.
In c.980, Tawhidi, penned Borrowed Lights (al-Muqabasat), a philosophical book, wherein he refuted astrology, and outlined a simplified and vulgarized neo-Platonism, influenced by Gnostic elements, with four hypostases: god, intellect, soul, and nature. A large part of this work is devoted to the soul:
- “Many paragraphs of Borrowed Lights are devoted to the human soul, concerning which al-Tawhidi takes up positions that can be defined as Platonic. The soul subsists by itself and is not tied down to the body; on the contrary, it uses the body as an instrument. The soul does not arise from the mixture of the elements; thus the Galenic theory is implicitly rejected, although it is ascribed in one passage to Zeno (probably meaning the Stoic) (see Galen; Zeno of Citium). The union with the body is described as a kind of fall in a way which has clear antecedents in some soteriological conceptions of Gnosticism and Neoplatonism (see Gnosticism; Neoplatonism). In the course of the soul's descent from the heavenly realm it became covered in scales or veils, which it will cast off after physical death, that is, when it relinquishes the body. The soul becomes like a rusty mirror; just as the latter is no longer capable of reflecting external objects, the soul forgot what it knew in the intelligible world. Its true nature is also more fully active in sleep. In our ordinary waking life, we do not remember the world where our soul originated because we have been overcome by matter. These two states of the soul, incarnate and immaterial, correspond to the two realms of intellection and sense-perception. Intellection is an immediate form of apprehension, devoid of reflection and deliberation, whereas sense-perception is linked to discursive and inductive modes of thought, such as syllogism.”
- — Charles Genequand (1998), Routledge 
Family | Name
Tawhidi was born into a poor family that sold dates called tawḥīd (hence his surname). Others, however, say that his "date name" was a mark of his adherence to “mutazilism”, the members of this group called “people of uniqueness and justice”. His parents are said to have died when he was young, after which he spent much of his childhood as an orphan in the care of his uncle, who treated him poorly.
In 1985, after Ibn Sa'dan died, Tawhidi seems no longer to have found such a rewarding place, and to have suffered from a lack of recognition of his talent, so much so that at the end of his life he burned his own books in a gesture of bitterness.
Quotes | On
The following are quotes on al-Tawhidi:
- “Tawhidi is the philosopher of men of letters and the man of letters of philosophers. ”
- — Yaqut al-Rumi (c.1220), Publication
- “The three worst zindiqs [anti-religionist radicals] of Islam, according to Islamic literary tradition, were: al-Rawandi, al-Tauhidi, and al-Mararri.”
- — Jennifer Hecht (2004), Doubt: a History (pg. 231) 
Quotes | By
The following are quotes by al-Tawhid:
- “Inexperienced people think that books will lead the one of intellect to understanding. But the ignoramus doesn't know that in these books are ambiguos that will confuse even the most intelligent of people. If you try to learn this knowledge without a teacher you will go astray and affairs will become so confusing to you that you will be more astray than Toma, the physician.”
- — al-Tawhid (c.1000), Publication 
- Zindiq – DarkFiber.com.
- Warraq, Ibn. (1995). Why I Am Not a Muslim (pgs. 259-60). Prometheus.
- Abu Hayyan al-Tawhidi (French → English) – Wikipedia.
- Margoliouth, David. (1905). Mohammed and the Rise of Islam. Putman.
- Heck, Paul. (2013). Skepticism in Classical Islam: Moments of Confusion (Tawhidi, 5+ pgs). Routledge.
- Genequand, Charles. (1998). “al-Tawhidi, Abu Hayyan (c.930-1023)”, Routledge, MuslimPhilosophy.com
- Hecht, Jennifer. (2004). Doubt: a History (pg. 231). Publisher.
- al-Tawhidi quote – GoodReads.com.