Avicenna

Early Life

Avicenna was born in 980 CE near Bukhara (in modern Uzbekistan), in the Samanid domains of Central Asia. He was a child prodigy of staggering proportions: he had memorized the Quran by age ten, mastered logic and mathematics by fourteen, and surpassed his teachers in philosophy and medicine by sixteen. He reportedly read Aristotle's Metaphysics forty times without understanding it, until al-Farabi's commentary unlocked it for him.

By eighteen, Avicenna was a fully qualified physician. He was summoned to treat the Samanid ruler Nuh ibn Mansur, and as a reward was given access to the royal library — one of the greatest in the Islamic world. He described himself as having mastered all the sciences by the age of twenty-one, after which 'I did not add anything essential.'

Career

Avicenna's life was extraordinarily turbulent. He served as physician and advisor to various rulers in Iran and Central Asia, moving from court to court as political circumstances changed. He served twice as vizier (chief minister) and was imprisoned more than once. He continued writing throughout these upheavals — reportedly composing parts of the Shifa' while in hiding, on horseback, and even in prison.

He died in 1037 CE in Hamadan (modern Iran) at the age of fifty-seven, reportedly from a stomach ailment (possibly colic or intestinal cancer), having exhausted himself through overwork and, according to some accounts, excessive indulgence.

The Distinction Between Essence and Existence

Avicenna's most original and consequential metaphysical contribution is the distinction between essence (mahiyya) and existence (wujud). The essence of a thing — what it is — does not include or entail its existence. Knowing what a horse is (its essence) does not tell you whether any horse actually exists. Existence is something added to essence from outside — from a cause.

This leads to Avicenna's fundamental metaphysical distinction:
- The Necessary Existent (wajib al-wujud): A being whose essence includes its existence — it cannot not exist. This is God.
- Possible existents (mumkin al-wujud): Beings whose essence does not include existence — they might or might not exist. Every possible existent requires a cause for its existence.

This distinction — one of the most influential ideas in the history of philosophy — was adopted by Thomas Aquinas (as the real distinction between essence and esse) and became foundational to Western metaphysics.

The Proof for God's Existence

Avicenna's proof begins from the concept of possible existence. Every possible existent requires a cause. If that cause is itself possible, it too requires a cause. This chain cannot go on to infinity (Avicenna argues against infinite causal regress). Therefore, there must be a Necessary Existent — a being that exists by its own nature and is the ultimate cause of all possible existents. This being is God.

The Flying Man

Avicenna's 'Flying Man' thought experiment anticipates Descartes' cogito by six centuries. Imagine a person created in mid-air, blindfolded, with limbs spread so they touch nothing — receiving no sensory input whatsoever. Would this person be aware of their own existence? Avicenna argues yes: even without any sensory experience, the soul is directly aware of itself. This proves that the self (the soul) is known independently of the body and is therefore not identical with it.

The Canon of Medicine

Avicenna's al-Qanun fi al-Tibb (The Canon of Medicine) is a five-volume medical encyclopedia that systematized Greek, Roman, and Islamic medical knowledge. It was translated into Latin in the 12th century and used as the primary medical textbook in European universities from the 13th to the 17th century — one of the most influential medical texts ever written.

Legacy

Avicenna's influence is almost impossible to overstate. In the Islamic world, his philosophical system became the framework within which all subsequent philosophy was conducted — even his critics (notably al-Ghazali) worked within categories he defined. In the Latin West, his metaphysics shaped Aquinas, Duns Scotus, and the entire scholastic tradition. His medical writings dominated European medicine for half a millennium. He wrote over 400 works, of which approximately 240 survive.