- Meditations on First Philosophy by Descartes


In the early 1600s Descartes studied in the Jesuit College of La Flèche for several years. The curriculum consisted of Latin and Greek grammar and literature with a further three years of philosophy, which meant Aristotle. Mathematics was also part of the course. 

When Descartes came to write his philosophy he based it on a complete revamp of the traditional scholastic Aristotelianism learned during his schooldays.

The first break with medieval Aristotelian philosophy was his rejection of substantial forms as a basis for physics. One example is the swallow bird. Its substantial form is "swallowness" and that format allows it to catch insects on the wing and fly. Descartes agreed that this was true but objected that it neither said anything new or useful about swallows. In short this sort of thinking was of no use in discovering new knowledge. Scholastic Aristotelian philosophy was metaphysics founded on physics; Descartes' philosophy was physics founded on metaphysics.

In place of substantial forms the author proposed mechanistic principles. These used deductions from the configuration and motion of parts. (There is a story which tells of how Descartes constructed an automaton in the shape of a young girl. Some writers interpret this as an attempt to show that the physical body works like a machine and that animals are soulless automata.)

He also rejected Aristotelian substantial forms and final causes because they confused body and mind. He uses the gravity of a stone as an example. Scholasticism explains that the stone knows its goal is the centre of the earth and the path to take. Descartes insists that it is an error to ascribe a mental aspect like knowledge to something physical. He argues that the idea of the mind should be differentiated from that of the body.

Another criticism that Descartes directed against Aristotelianism was his rejection of the thesis that all knowledge came from sensation. Descartes affirmed that the senses can be deceived and thus are unreliable sources of knowledge. He preferred to replace premises based on sensation with ideas from the mind alone. 

Descartes wrote Méditations métaphysiques (1641) in Latin when in Leiden, Netherlands. Hoping to gain a wider audience it was later translated into French and published in 1647. In his quest for a solid basis on which to build philosophical truth he decided to approach the problem discarding as false any concepts that had a shadow of doubt. However, he soon began to realise that through this method existence itself came into doubt. 

Dreaming and day dreaming were proofs for Descartes that our senses are not to be trusted. We might be hallucinating everything we experience. Thus he dismisses sensory experience as a true basis for philosophy since if our senses can mislead us some of the time they may well mislead us always. But if we cannot trust our senses how can we know that the external world really exists?

"So serious are the doubts into which I have been thrown as a result of yesterday's meditations that I can neither put them out of my mind nor see any way of resolving them. It feels as if I have fallen unexpectedly into a deep whirlpool which tumbles me around so that I can neither stand on the bottom nor swim up to the top."

Searching around for some support base he hit on "Cogito ergo sum" which might be translated "I am thinking therefore I am." You cannot doubt the existence of your own thinking because if you are doubting you are thinking. The solid base then is the existence of the thinking mind.

From this sceptical foundation Descartes then rebuilds human knowledge and in his book even puts forward proofs for the existence of God. However, through his method of doubting external existence the author unwittingly creates a divide between the mental world (thinking) and the physical one (existence). He is sure of the mental part but unsure of how it relates to the physical.


There are 6 meditations plus an introduction in Meditations on First Philosophy (1641) first published in Latin. Following a tradition which dates back to Renaissance Italy he published a vernacular version in French aimed at allowing a wider public to read the work. The author's aim in the book was to ascertain what could be known with certainty.

The introduction consists of a dedicatory and preface. Descartes addresses the Parisian faculty of theology to explain that the existence of God needs a philosophical demonstration. He also reminds the reader that if something perfect can be imagined then it must exist.

First meditation: Descartes reviews the false ideas he has held in his life and decides to doubt anything which he cannot prove to be true. For this he relies on a belief in sensory information as trustworthy. He takes the example of dreaming and concludes that if dreams can deceive his senses then an omnipotent God could do the same. To avoid deception, which may come from a source of evil, he determines to doubt everything he previously held as true.

Second meditation: The author plans a way of thinking he calls "representationalism". It affirms that we have ideas which are represented in memories, beliefs and other ways. They may be true or false. These representations disconnect the mind from reality but he insists that there must be a connection between mental thought and experiences. He resolves that if he can imagine himself thinking then he exists and the statement "I am, I exist." must be true.
"I" is defined as wax which we perceive through its waxiness. In the same way "self" is not an sensory experience but a perception of ourselves as distinct. He is an object that thinks.

Third meditation: Descartes proposes that the existence of God can be proved using philosophical reasoning. He reasons that he is imperfect but can conceive of a perfect being. Therefore that being must exist. Perfection also implies benevolence so this being would never deceive him.
Basing himself on a belief that everything has a source he reflects on the source of his own existence. It cannot come from imperfect sources such as his parents or himself since they depend on others to come into being so the idea of perfection must come from the existence of God. 

Fourth meditation: This section argues that humans exist between the perfection of God and the nothingness of evil. We cannot grasp the mind of the perfect being yet we act without taking this into account, so through our free will we may fall into error.

Fifth meditation:  Descartes discriminates between clarity and obscurity of thought. Mythical creatures are creations but triangles will always have a sum of 180 distributed between their angles. Thus some external things are fixed in nature. In a similar way existence is inconceivable without God. Perfection and God go together and existence includes perfection so God must exist.

Sixth meditation: The meditator attempts to explain the existence of external physical objects without reference to sensory experience which he finds unreliable. He reasons that imagination and sensory perception are modes of thought. He could conceive of himself without imagination or sensory perception, so they are not essential to him, but imagination and sensory perception could not exist without a mind to contain them. Mind is necessary sensory perception and imagination are contingent. 
He proves that mind and body are distinct because God created the mind independently and it can exist without the body. God is not a deceiver and created the senses through which we perceive the external world so it must exist.



Descartes begins in the First Meditation by asking himself how he can be sure of anything. This has marked his own methodology and the thinking of future philosophers with a sceptical outlook towards claims of any knowledge. This may derive from the author's high standard for what constitutes knowledge which he argues cannot be based alone on sensory experience.

“But to then I only wanted to go about seeking the truth, I thought it was necessary for me to do just the opposite, and that I reject as absolutely false everything in which I could imagine the least doubt, to see if it would point, after that, something in my belief, that was entirely indubitable”

The Second and Third Meditations propose reason as a substitute for the sensory as a foundation for our beliefs in sensory input. He uses reason to establish his own and God's existence which allows him to proclaim that we are not deceived by the outside world. This is true because God, the perfect being, would not deceive us. 

The Existence of God

Descartes argues that we would not have the idea of God if God did not exist to cause this idea. Therefore God must exist.
This thinking is known as the Cartesian circle: to establish certainty about reasoning we must establish that God exists, but to establish that we need to establish certainty about reasoning.
However, God does allow us to be deceived about reality. Since the author holds that colours, smells and others sensory attributes are added by us to objects perceived. They are illusions. If God allows this deception why not more?

Augustine of Hippo and Descartes

In the Third Meditation Descartes emphasises the idea that we are made in the image of God. The author probably got this idea from Augustine's City of God

"And we indeed recognize in ourselves the image of God, that is, of the supreme Trinity, an image which, though it be not equal to God, or rather, though it be very far removed from Him,—being neither co-eternal, nor, to say all in a word, consubstantial with Him,—is yet nearer to Him in nature than any other of His works..."

Descartes concept of sensory experience is also remarkably similar to that of Augustine writing in the 5th. century > 

"... for we do not come into contact with these by some bodily sense, as we perceive the things outside of us,—colors, e.g., by seeing, sounds by hearing, smells by smelling, tastes by tasting, hard and soft objects by touching,—of all which sensible objects it is the images resembling them, but not themselves which we perceive in the mind and hold in the memory, and which excite us to desire the objects.  But, without any delusive representation of images or phantasms, I am most certain that I am, and that I know and delight in this."

Augustine's idea of being also approximates closely to Descartes' later certainty of "I am":

"In respect of these truths, I am not at all afraid of the arguments of the Academicians, who say, What if you are deceived?  For if I am deceived, I am. For he who is not, cannot be deceived; and if I am deceived, by this same token I am.  And since I am if I am deceived, how am I deceived in believing that I am? for it is certain that I am if I am deceived."

Mind and Body

Descartes clearly thought that the difference between mind and body was so great that he questioned how they could affect one another. For the author matter has spatial attributes such as length, height, weight and so on. The mind has none of these spatial characteristics but is conscious. 

"The whole problem contained in such questions arises simply from a supposition that is false and cannot in any way be proved, namely that, if the soul and the body are two substances whose nature is different, this prevents them from being able to act on each other."

Descartes solution to the problem was that mind and body had different principal attributes: consciousness and extension. He proposed that they interacted through the pineal gland. However, the pineal gland is physical and if the problem is how the mind can interact with a physical entity then this does not solve the problem because the pineal gland is a body part. 
Descartes solution to his own problem is unacceptable but it has left philosophy with the inheritance of this clear Cartesian distinction between mind and body as an ongoing problem. We experience colour differently from the real electromagnetic radiation that produces it. We distinguish sharply between physiology and psychology but see no way to connect them.


Descartes is a rationalist thinker as contrasted with Aristotle or the British empiricists' approach. He asserts that the intellect is the only means of arriving at  knowledge with certainty. The senses he considers to be of practical use in moving through the world, but not trustworthy  enough as bases for knowledge.

In order to he able to trust knowledge obtained through reason three conditions are needed: belief, truth and justification.
Reasoning allows you to detect and eliminate false facts and justify the true ones.
Descartes  offers wax as an example. Our senses smell, see and feel the wax, but if we heat it the substance liquefies and changes its texture and touch. It is thus possible to deceive sensory information and our knowledge of the object is also uncertain. To understand wax you must strip away all its sensory information and that leaves you with a rational grasp which is flexible, changeable and extendable. All of its attributes are understood only in the mind. It is through the mental faculties that we best acquire knowledge.

Descartes as Influencer

Descartes' theory of knowledge has its roots in Galileo's division between primary properties of material things (size, shape, position, movement) which are intrinsic to them and secondary properties (colours, touch, sounds, smells, tastes) which only exist in the mind.

Ever since Descartes philosophers have been working to bridge the Cartesian gap between mind and body and also to analyse the essence of Cartesian thought: "Pienso luego existo."

Malebranche in his De la recherche de la vérité (1674-75) proposed the theory of occasionalism to explain the cartesian division between mind and matter. This stated that when humans interact with their external environment God supplies the sensory ideas in the mind. It is also God who makes humans move. God is then the intermediary between the mental and the material. Malebranche embraced the Platonic view that ideas of reality reside in God and occasionally God illuminates these ideas for humans.

Spinoza's work Ethics (1677) offered a synthesis of mind and matter in one substance which is both God and the world. Humans only know the mental and the physical though there exists an infinite number of other attributes in the world. Attributes are parallel since every idea has its physical attribute and vice versa. Mind and matter do not interact.

Leibniz in his Monadology (1714) also suggested a parallelistic solution to the mind/body relationship. His model rests on monads which populate the universe in infinite numbers and each perceive it from their own point of view. There exists a harmony among them maintained by God. This ensures an apparent interaction among them in the material sphere.

Berkeley, the Irish bishop, in his Treatise on Human Knowledge (1710) took a radical empirical view on the Cartesian division of mind and matter. He simply denied that matter existed. He described material things as collections of sensory ideas presented to humans by God. All ideas are revealed directly.

Hobbes, in contrast to Berkeleyasserted that only matter exists in Leviathan (1651). He equated brain and mind so that ideas are simply motions of brain matter. The material mind can thus cause bodily motions and, as ideas are material, they can represent physical realities.

Locke argued in his  Essay Concerning Human Understanding (1690) that the secondary properties are the result of interaction between the primary properties of objects and the human senses. He insisted, however, that our sensory perceptions resembled reality's primary properties and so were a source of knowledge about them. He gave a concrete example of this concept using a bus as the object. The primary qualities of an object, such as the solidity and occupation of space exist independently of the perceiver. The secondary ones, like the colour, differ according to what he perceives. For example, if we jump in front of a red bus whose primary qualities are solid and take up space, it will cause injury and possibly death. The way the bus appears to us is a controlled hallucination; the bus itself is not. Cartesian theory remains sceptical that mental ideas can in any way be like material objects.

Hume, in his Treatise on Human Nature (1737), analysed the self, the Cartesian "I", and stated: "I may venture to affirm the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement." We are only aware of momentary experiences, not of a 'self'. Memory allows us to connect our feelings and ideas but leaves no evidence of any essence. Hume proposes that the self is just an assortment of perceptions, links in a chain, so that to look for a core is to search for a chain without the links. Self, he argues, is the fruit of our habit of assigning sense to a collection of patterns. This is natural but not logical. The Cartesian "I" in "I think" is, according to the author, a construction, not a stable element.
Hume also questioned the "therefore" in Descartes' slogan "I think therefore I am." In fact he denied any external causality saying that cause and effect were mental perceptions, not realities. "There is a very remarkable inclination in human nature to bestow on external objects the same emotions which it observes in itself, and to find everywhere those ideas which are most present to it."  Hume allows that we perceive two events that apparently happen at the same time but he insists that we cannot know their relationship. He explains this through our mental habit of association which he thinks is an unfounded belief, not a fact, and as so meaningless. The author agrees that we have an instinctive belief in causality through our habits but that we cannot prove nor discount this belief.

Kant argued against the one-sided view of the Cartesians for a synthesis between experience and rationalism in his Critique of Pure Reason (1781). "Experience without theory is blind, but theory without experience is a simple intellectual game." 
On the one hand, empiricism admits synthetic propositions and a posteriori knowledge; on the other hand, rationalism admits analytical propositions and a priori knowledge. Kant maintained that the two could be combined, that synthetic a priori statements were possible and that there were propositions that applied to, but did not derive from, the physical world but were established by negotiation. He argued that knowledge resulted from a synthesis of experience and concepts. Without the senses we would not be aware of an object and without understanding and reasoning we could not form a concept of it.
The author also analysed the "think" concept in Descartes' summary phrase in an original contribution to the philosophical tradition. This was the idea that it is representation that makes the object possible rather than the object that makes representation possible. This introduced the concept of the human mind as an active creator of experience, rather than a passive recipient of perception, and put the role of the human subject, the knower, at the centre of the study of how we know.
However, he agreed with the Cartesian distinction between appearance (phenomena) and reality (noumenon). We know through our senses that the material world exists but its real substance remain unknowable. We have certain predispositions about what exists and only the things that fit into these exist for us.

Husserl tried to construct a science of sensible ideas called phenomenology. 

Russell and his student Wittgenstein between the 19th and 20th centuries understood aspects of the physical world as logical constructions of sense d

James at the end of the 19th century in the USA followed the pragmatist philosophy suggesting that mind and matter could both be constructed out of neutral monads.

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