Descartes: rationalism and cogito ergo sum

“I think, therefore I am”. On the one hand Descartes‘ thesis tends to elicit reactions of awe, on the other bewilderment at why someone would attempt to prove something so obvious. But, before one can understand the importance of Descartes’ conclusion cogito, ergo sum, it is essential to understand Descartes epistemology.

Descartes was a rationalist – in his work he uses methodological skepticism to undermine the certainty of knowledge gained by sensation. As an example, Descartes offers his “evil genius doubt” thesis, in which he postulates that it is possible that a powerful and evil demon has given him flawed faculties. Thus Descartes argues that even the most supposedly simple and evident matters must be called into question.

However, there are some matters of which one can be sure. For example, one must be doubting of something or doubt that they are doubting. Doubting requires thinking – thinking requires a thinker – ergo, “I think, there I am”. For the evil genius to be a deceiver, it takes something to be deceived. As a further example, take Descartes’ thesis in reverse: “I don’t think, there I am not”. Clearly it is false, for it requires thinking to think that one does not think.

Even though Descartes found a use for skepticism in his method, he is not an extreme skeptic such as the likes of Pyrrho. According to Descartes, ideas such as 3 + 3 = 6 or triangles have three sides are knowable. In fact, these ideas are known innately (hence Descartes’ rationalism).

Does any of this sound familiar? Descartes’ thought experiments are eerily similar to Plato’s allegory of the cave. And this is precisely the Cartesian criticism of the Aristotelian-Scholastic tradition, that like the prisoners of the cave they have become overly dogmatic regarding the power of sensation and have confused substance for shadow and shadow for substance.

Rene Descartes: Introduction

Rene Descartes (1596 – 1650) was a French philosopher and mathematician. The general consensus is that he is the father of modern philosophy (or at least its most prominent philosopher). Like Aristotle and Plato, his texts (particularly Meditations on First Philosophy) continue to be used as standards at many universities today.

Descartes desired to write philosophy “as if no one had written on these matters before”. Arguably, this is the source of novelty in much of his work. However, the degree of originality of Descartes’ work is often under scrutiny, as many of what are considered distinctly Cartesian ideas can be found as proto-arguments in earlier philosophers such as Aristotle and Augustine.

The three most influential ideas and works of Descartes can be summaried as follows:

1. His use of doubt (i.e. methodological skepticism) to indelibly prove the existence of the human mind with his argument cogito ergo sum “I think, there I am”. His skepticism of the existence of the body lead ultimately to his dualist theory of mind and the modern mind/body problem.
2. His discovery of the link between algebra and geometry, and the subsequent development of analytical geometry where geometrical problems are expressed and solved mathematically. The Cartesian cooridinates are named after Descartes, and the convention of calling points a,b,c and x,y,z is a carryover from Descartes’ work.
3. Following from the development of analytic geometry, Descartes re-envisioned matter as only possessing the primary property of extension – in other words, matter is simply something that “takes up space”. This mathematicised view of matter enabled the modelling of reality using algebraic equations. This innovation was implicitly a rejection of the Aristotelian-Scholastic orthodoxy of physical substance as a composite of matter/form, and any appeal to final causes or ends as explanations for natural phenomena.

Averroes and Aristotelianism

Avicenna created a synthesis of Islamic and Neoplatonic thought that was enormously influential during the height of the Islamic Golden Age. Fearing the pollution of Islam from the syncretism of pagan thought, Al-Ghazali criticised Avicenna harshly in his work the Incoherence of the Philosophers.

Averroes was born in Spain (which was under Islamic rule) in the year 1126 AD. Like Avicenna and Al-Ghazali he was a polymath, writing broadly and excellently on many subjects such as medicine, politics, law, science and etc. He devoted the final thirty years of his life to philosophical works, and in particular to a study of the works of Aristotle; producing some known twenty-eight philosophical works as original ideas and commentaries on Aristotle.

Averroes’ most popular work was called the Incoherence of the Incoherence, a polemical title that indicates the books criticism of Al-Ghazali. Averroes attacked Al-Ghazali on two accounts. The first was that Avicenna’s synthesis of Islamic and Platonic thought was not an accurate representation of the work of a philosopher and thus Al-Ghazali had not attacked the strongest possible opponent. Secondly, that Al-Ghazali’s arguments themselves were prone to error.

Averroes argued that a harmonious relationship between philosophy and faith could be achieved because they operate in separate spheres. In this manner, Averroes’ criticism of Al-Ghazali is that it is possible for both Aristotle to be correct and the Qu’ran to the be the eternal truth of God.

Avicenna and the floating man experiment

St. Augustine was responsible for re-appropriating the intellectualism of Classical Greece through his synthesis of Platonic Christianity. The Islamic world would also experience its own halcyon days, called the Islamic Golden Age.

From 750 to 1250 AD, Islamic philosophers and scientists made significant advances in the fields of scientific knowledge, arts and culture. As with medieval Christianity, this was achieved through the reinterpretation of earlier traditions with the innovation of the new religion of Islam.

The foremost of these philosophers was the Persian polymath Avicenna, who was born in 980 AD in Iran. He is thought to have wrote approximately 450 treatises on a variety of topics including medicine, philosophy, chemistry, astronomy, Islamic theology and metaphysics. His most popular works are the Book of Healing and the Canon of Medicine, where he developed a systematic approach to medicine in the style of Hippocrates – both of these volumes were used as textbooks in universities for hundreds of years (until around 1650).

His most famous philosophical contribution is the “floating man experiment”, which is eerily similar to Augustine’s refutation of the skeptics. Avicenna asks his readers to imagine themselves as floating disembodied men with no sensory connection to the external world. Avicenna argues that these disembodied men would still possess self-awareness. In the Aristotelian tradition, Avicenna says that because the floating man is able to determine his own existence, then the soul must then be a type of immaterial perfection that is not dependent on the potentiality of physical and material things. As a possible precursor to the modern Cartesian view of man, Avicenna contends that the body is unnecessary to the soul which is a type of immaterial substance.

Augustine and cogito ergo sum (I think, therefore I am)

Descartes is famous for his philosophical conclusion cogito ergo sum, or in English “I think, therefore I am.” Descartes, who believed that the mind and body were separate substances, asserted that the cogito ergo sum proved most certainly the existence of any mind who thought it – but not the mind’s body or the things the mind is perceiving.

Descartes was not the first philosopher to outline the ideas behind his cogito ergo sum. Plato speaks of having knowledge of knowledge or “justified true belief”. Aristotle, in his Nimochean Ethics, says that whenever a thinker, seer or perceiver is conscious of their experience of thinking, seeing or believing they must be conscious of their own existence.

During Augustine’s era Plato’s Academy had undertaken a radical turn towards skepticism. Augustine dabbled in academic skepticism for a time, but turned from it following his conversion to Christianity. Later he would argue against the Academics, and the cornerstone of his argument is a thesis almost identical to Descartes’ (which would follow some thousand years later).

The skeptical claim at its heart was that one could not be certain of anything. Using argumentum ad hominem, Augustine accepts their premise of uncertainty and refutes it by pointing to the fact that one cannot be mistaken and not be at the same time – “If I am mistaken, I am”. He goes further in the Enchiridon:

By not positively affirming that they are alive, the skeptics ward off the appearance of error in themselves, yet they do make errors simply by showing themselves alive; one cannot err who is not alive. That we live is therefore not only true, but it is altogether certain as well.

Chapter 7 section 20