Sajjad Rizvi

Abu ‘Ali Husayn ibn Sina, better known in Europe as Avicenna, is arguably the most influential philosopher of the pre-modern era. Born near Bukhara in Central Asia, he is best known as a physician whose major work the Canon continued to be taught as a medical textbook in Europe and in the Islamic world until the early modern period, and as a philosopher whose major work the Cure had a decisive impact upon European scholasticism.

Avicenna is well known as the author of one of the most influential proofs for the existence of God. The argument runs as follows. Our perceptual experience of the world confirms that things exist, and that their existence is non-necessary because we notice that things come into existence and pass out of it. Existence that does not exist by virtue of itself cannot arise unless it is made necessary by a cause. A causal chain must culminate in one un-caused cause because one cannot posit an infinite series of causes. Therefore, the chain of existents which do not exist through themselves must culminate in and find its causal principle in a sole self-subsistent existent that is necessary. This, of course, is the same as the God of religion.

Avicenna’s theory of knowledge was also highly influential. According to him, humans were not born with any innate knowledge of the world. Humans attain knowledge and understanding through acquaintance with and experience of objects in the world. From those experiences, they abstract universal concepts. For example, you see a horse and note what properties and features it possesses. From this experience, you derive the concept of a horse and when you encounter another object with similar features, you recognise it to be a horse. More complex notions and knowledge require that you add together concepts abstracted in the mind to produce further concepts. Observations lead to the formulation of concepts; amalgamation of concepts leads to the formulation of more complex concepts. Take the example of the horse again. We can understand more complex concepts of a horse depending on, say, its uses or its colour, or its species.

The most important question which arises is, how can we verify that the concepts we have abstracted from our experiences are correct? How can we say that it is true that a horse is always an animal with four legs for example? According to Avicenna, there are two ways of verifying our claims. First, we must correctly extrapolate concepts from our experiences and arrange those concepts in a form of argument which is valid in order to produce complex concepts. Second, we must guarantee that we are not mistaken in our experience and that our concept of a horse is indeed a valid concept. That guarantor must be independent of the ability of humans to make mistakes; it must be infallible and must transcend our experiences and our world, drawing its knowledge of things from their absolute source in a higher perfectly intelligible world, of which our world is a weak image. Avicenna calls this transcendent guarantor and source for human knowledge, the Active Intellect. This higher source illuminates the human mind and bestows upon it true knowledge through an act of conjunction whereby the human mind encounters the higher mind in episodes where it seeks verification of what it knows. As the Active Intellect is linked to the perfect knowledge of God, it is ultimately God who bestows true knowledge upon humans.

Avicenna's epistemology is predicated upon a theory of soul (or an inner essence that in modern parlance might be called a 'self') that is independent of the body and capable of abstraction. This proof for the soul in many ways prefigures the Cartesian cogito by some 600 years. It is the so-called 'flying man' argument or thought experiment. If a person were created in a perfect state, but blind and suspended in the air but unable to perceive anything through his senses, would he be able to affirm the existence of his soul? Suspended in such a state, he cannot affirm the existence of his body because he is not empirically aware of it, thus the argument may be seen as affirming the independence of the soul from the body. But in that state he cannot doubt that his soul exists because there is a subject that is thinking, thus the argument can be seen as an affirmation of the self-awareness of the soul. This argument does raise an objection, which may also be levelled at Descartes: how do we know that the knowing subject is the soul?

Avicenna’s major achievement was to propound a systematic philosophical defence of religion rooted in the theological tenets of Islam, and its success can be gauged by the recourse to Avicennan ideas found in the subsequent history of philosophical theology in Islam. In the Latin West, his metaphysics and theory of the soul had a profound influence on scholastic arguments and, as in the Islamic east, were the basis for debate and argument until the early modern period.

Suggested reading
Goodman, L. E. 1992. Avicenna. London: Routledge.
Gutas, D. 1988. Avicenna and the Aristotelian Tradition. Leiden: Brill.
Street, A.D. 2004. Avicenna. Cambridge: The Islamic Texts Society.