Aristotle and Ibn Sina on Knowledge

How do we know what we know? And what is it within us that acquires knowledge? Ibn Sina is arguably the most influential philosopher working in the Islamic intellectual tradition. For Ibn Sina, the foundations of epistemology – the philosophy of knowledge – are found in Aristotle.

This article begins with a brief explanation of Ibn Sina’s overall philosophical project. It then moves on to a brief analysis of Aristotle’s approach to knowledge, to set the scene of Ibn Sina’s own theory. What follows is a two part analysis of Ibn Sina’s theory of knowledge, focusing first on his rationalism and logical theory, and second on his empiricism and theory of perception.

What were Ibn Sina’s philosophical ambitions? Ibn Sina’s overriding philosophical aim was to create a philosophical system which constitutes a self-contained whole. This meant reconciling rational philosophy with the prevailing Islamic orthodoxy of his time. As per Dimitri Gutas, Ibn Sina held that,

“The task of presenting and writing about philosophy as an integral whole and not piecemeal and occasionalistically; bringing philosophy up to date; and studying how the human soul (intellect) knows as the foundation of his theory of knowledge, logical methodology, and the relation between the celestial and terrestrial realms, or the divine and human.”

His attempt to do this was closely modelled on an Aristotelian framework, who similarly had a strong sense of the unity of philosophy, as set out on the logical structure exhibited in (e.g.) Posterior Analytics.

Aristotle’s Theory of Knowledge

Indeed, there is no better place to start on Aristotle’s theory of knowledge than with the Posterior Analytics, for it is here that many of Aristotle’s main theses on knowledge are stated most clearly. It begins with the following claim:

“All teaching and all learning of the discursive sort arises out of pre-existent knowledge.”

This appears to echo the Platonic doctrine of recollection, as stated in the Meno “Every piece of knowledge arises out of some pre-existent knowledge”. This is often understood as indicating that Aristotle is an anti-foundationalist.

What is foundationalism? Foundationalism is the view that all of our beliefs fall into two categories: basic and non-basic. Basic beliefs are the foundation of non-basic beliefs. Basic beliefs are therefore those which do not rely on any further belief – they are true by virtue of themselves, they alone establish their own truth. This is the principle of doxastic basicality. However, this will eventually be used to support a foundationalist theory, in particular one which rests on a special kind of knowledge, which Aristotle calls ‘knowledge simpliciter’.

Aristotle holds that we do not really know what is true until we have established why it is true, and to establish why something is true is to offer a syllogistic demonstration of it (A if B, B if C, so A if C).

Aristotle holds that if all knowledge is demonstrative knowledge, then either these demonstrations are infinite or they are circular. As Aristotle takes it as a basic truth that there is knowledge (i.e. demonstrations cannot just run on forever), and that circular demonstration isn’t possible, he therefore concludes that not all knowledge is demonstrated knowledge, and that all demonstrated knowledge rests on premises which are known, and yet not demonstrated.

The question then is how the knowledge which is known but not demonstrated – that is, knowledge consisting of ‘basic beliefs’ – is established. The complication is that Aristotle’s attempt to explain this – in the final chapter of the Posterior Analytics – appears in two parts, the first of which tends to elicit an empiricist interpretation and the latter of which a rationalist one.

Generally, the attempt to reconcile these two elements of Aristotle involves taking him as a rational empiricist. The idea is that while some knowledge is derived from indemonstrable principles taken from experience, we do not understand reality as a whole purely from experience without the application of reason.

Often, Aristotle’s epistemology is understood in contrast with that of Plato. Plato believes that experience deceives us, and philosophical enquiry allows us to avoid being misled by it in order to understand things in themselves. Aristotle believes that, in order to understand things in themselves, we must reason from experience.

Ibn Sina’s Mode of Reasoning

It is worth saying something about Ibn Sina’s mode of reasoning, which structures his philosophical project overall. The central inferential mode in Ibn Sina’s work, as it was for Aristotle, is the syllogism, which Dimitri Gutas helpfully summarizes as follows:

“There being three terms in a syllogism, two of which, the minor and the major, are present in the conclusion, the syllogism that leads to that conclusion can be constructed only if one figures out or guesses correctly what the middle term is that explains the connection between the two extreme terms.”

In other words, if we seek to verify the statement “A is C,” we must look for a suitable B to construct a syllogism of the form, “A is B, B is C, therefore A is C.”

This is the method by which things which are in themselves opaque to us (that is, C) can nonetheless become accessible by the application of rigorous logic.

If Ibn Sina’s rationalism – his belief in the place of logical inference in human understanding – invested him with a profound interest in logic, then his empiricism is a large part of what drove him to investigate the human soul, which for Ibn Sina included investigating much of what we would casually refer to as the mind.

Senses, for Ibn Sina, are not merely external. He enumerates the five external senses much as we do today (sight, taste, touch, hearing, smell), but also a matching set of internal senses: common sense, imagery (where the forms of things are stored), imagination, estimation (judging the imperceptible significance or connotations for us of sensed objects, like friendship and enmity, which also includes instinctive sensing), and memory.

Moreover, he is especially concerned with how our perception (internal and external alike) can help or harm our efforts to determine the middle term of syllogisms – that is, the term which takes us from what we already know to an understanding of things in themselves. Ibn Sina’s theory of knowledge owes much to his cosmological inheritance: that is, the combination of the Aristotelian model for the sublunar world, Ptolemaic general cosmology, and neo-Platonic emanationism in the supra-lunar.

Two Ways of Knowing 

We can distinguish two ways of knowing here. First, at a more basic level, the intellect constructs syllogisms with the aid of the internal and external senses. At a higher level, the level which Ibn Sina takes to be a perfection of the soul, thinking takes no time and grasps an object (along with its syllogisms) all at once.

This latter state can be acquired by practicing intellection using our senses and syllogism, until we acquire a kind of automatic intimacy with objects themselves. The highest form of this we see on Earth is the prophet, who acquires the intelligibles, “either at once or nearly so … in an order which includes the middle terms”.

The perfection of philosophy is its development into a flawless process of developing syllogism from experience. Sina develops this picture by explaining that the difference between human intellects and celestial intellects lies in the absolute potentiality of the human intellect, which requires actualization in the form of a body.

Indeed, of the three criteria Ibn Sina sets for whether someone is capable of acquiring knowledge of intelligibles – the humoral equilibrium of the recipient, the proper functioning of his internal and external senses, and the readiness of his intellect – two of them are explicitly bodily, and the third is also affected by embodiment.

That is because apprehending an intelligible is only possible for a limited period of time, because it is impossible for the immaterial intellect to store it. On the other hand, memory and imagery are capable of retention, given they have an actual location in the brain, which Ibn Sina takes to be necessary for retention.

The human intellect is rather an immaterial ‘effluence’ from the supernal world to that of human beings. Embodiment is both a method and a limitation (or, indeed, a method because it is a limitation) with respect to the apprehension of intelligibles. What this emphasizes is that the intelligibles are always available to human beings who are willing to follow through a thinking process fully.

Intelligibles and Syllogistic Reasoning 

Ibn Sina holds that in order to make the necessary syllogisms and abstractions from experience,

“The active principle [i.e. the active intellect] lets flow upon the [human rational] soul form after form in accordance with the demand by the soul; and when the soul turns away from it [the active intellect], then the effluence is broken off.”

Whereas the celestial intellects can know intelligibles directly from what causes them, human intellects rely on the senses to perceive the effect of intelligibles, and by way of syllogistic reasoning determine the cause. It is for this reason that Ibn Sina holds that, “the senses are the means by which the human soul acquires different kinds of knowledge (maʿārif )”, and it our predisposition to knowledge of principles of particulars and universals is actually the function of experiences.

Given that we progress from embodied, human intellects to disembodied, celestial intellects after death, we can conceive of Ibn Sina as theorizing a three-stage progression (albeit of an overlapping kind) between the use of experience, philosophical enquiry, and direct intellection of things in themselves.