Avicenna: Proof of the Truthful

By Gabriel Blanchard

By sustaining philosophy, Avicenna links the ancient and Scholastic worlds.

A Persian scholar who spent all his life in Central Asia, Avicenna is an exceptional figure in our author bank. This polymath not only engaged extensively with the great minds of the Greco-Roman world, but had an influence that reached across continents and spanned centuries. He laid some of the first foundations of modern medicine, and helped shape the development of Scholastic theology and philosophy.

Born in 980 in a village in modern Uzbekistan, Avicenna (the Latinized form of the Arabic name Ibn Sina) displayed a prodigious intellect from his early youthat the age of ten he had memorized the entire Quran, and by his teens he was studying mathematics, medicine, and philosophy. He went on to compose an encyclopedia, The Book of Healing, as well as a medical textbook titled The Canon of Medicine that remained in use for over six hundred years as far afield as Western Europe. He worked as a physician at multiple courts, and wrote volumes of commentary on Islamic theology, as well as on Aristotelian and Neoplatonic texts on logic, ethics, and proofs for theism. Despite the intervening continents, it was only a few decades after his death in 1037 that his encyclopedia, which included extensive discussions of philosophy and the sciences, reached the budding universities of the Scholastics.

Anyone who denies the law of non-contradiction should be beaten, until he admits that to be beaten is not the same as not to be beaten.

In particular, Avicenna advanced a form of the argument for the existence of God that remains influential to this day; he described it as “the proof of the truthful.” Reasoning from Aristotelian definitions, he identified all beings as either contingent (i.e., needing a cause in order to exist) or self-existent. Likewise, he said, the whole “set” of contingent beings had to either have a self-existent cause, or be self-existent itself; either way, a self-existent or necessary entity did exist. Building from there, he deduced further properties of this self-existent somethingthat it had to be singular, intelligent, and good, for instanceuntil he had arrived at a robustly theistic idea of God.

Not only Avicenna’s conclusions but his methodology appealed to the Scholastics. There was an “Avicennist” school of thought at the University of Paris in the twelfth century, and even after that was officially suppressed by ecclesiastical authorities, more orthodox luminaries like Aquinas and Duns Scotus continued to hew closely to his reasoning in many respects. Along with the handful of texts on logic the ancients bequeathed directly to the Medievals, his writings on logic impacted the curricula of the universities by both precept and example.

But Avicenna’s importance does not come solely from his influence on other thinkers. He represents the continuity of the Western tradition at what seem geographically to be its utmost fringes, during a time when Europe was half-drowned under centuries of invasions, religious strife, and plagues. The light of reason that we trace back to classical Athens was maintained and handed down by him; small wonder that Dante in his Inferno, though classifying Avicenna among the lost, places him in the dignified realm of Limbo alongside such luminaries as Virgil and Plato. It is no small thing to sustain the life of the intellect across centuries, and Avicenna is among the minds we have to thank for it.


Every week, we publish a profile of one of the figures from the CLT author bank. For an introduction to classic authors, see our guest post from Keith Nix, founder of the Veritas School in Richmond, VA.

If you enjoyed this post, you might also like our series on “the Great Conversation,” which discusses ideas from eternity to evolution to mathematics. Or take a look at our profile of St. Thomas Aquinas, one of the intellects influenced by Avicenna’s own work.

Published on 16th March, 2020.

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