1. Descartes' Meditations
Metaphysics and Epistemology
Chris Lindsay
University of Glasgow

2. The purpose of the Meditations
The purpose of the Meditations is twofold:
Epistemological: what can we know?
Metaphysical: what kinds of things exist?

3. Epistemology
Epistemology is the theory of knowledge: it concerns issues such as:
Can we know anything?
What can we know?
What means do we have of acquiring knowledge?

4. Means of knowledge acquisition
The senses:
Reason:

5. Metaphysics
Metaphysics is the study of existence. It involves questions such as:
What kinds of things exist in general?

6. Metaphysics What kinds of things (if any) exist in the external world?
What is the nature of the self?
Does God exist?

7. How are Epistemology and Metaphysics related?
If we want to claim that something exists, we should be able to give some account of how we come to have knowledge (or, at least, evidence) of its existence.
If we cannot show that our senses (or other means of acquiring knowledge) are reliable, then it undermines our grounds for claiming that those things they appear to give us knowledge of actually exist.

8. Descartes' epistemology
Descartes is a rationalist: he holds that all substantial knowledge comes through reason.
The main opposition to rationalism is empiricism: the claim that all substantial knowledge comes through experience.

9. Descartes’ rationalism
One of Descartes' greatest insights came in a dream on November 1619 about unifying the various sciences into one system of knowledge:
In the third dream, all was quiet and contemplative ... What was the idea that Descartes saw in a burning flash? He tells us that his third dream pointed to no less than the unification and the illumination of the whole of science, even the whole of knowledge, by one and the same method: the method of reason. (from Descartes' Dream, by Phillip J. Davis and Reuben Hirsh)

10. Descartes rationalism, again
Descartes was involved in the debate about which epistemology was appropriate for science.
Descartes wrote to his friend Mersenne:
I will say to you, just between us, that these six Meditations contain all the foundations of my Physics. But, please, you must not say so; for those who favour Aristotle would perhaps have more difficulty in approving them; and I hope that those who will read them will unwittingly become accustomed to my principles, and will recognise the truth, before they notice that my principles destroy those of Aristotle. (quoted in Hatfield, p. 25)

11. How much of what we previously believed is true?
Descartes' approach
The Meditations start with an epistemological issue:
How much of what we previously believed is true?

12. Descartes' starting point
Some years ago I noticed how many false things I had accepted as true in my childhood, and how doubtful were the things that I subsequently built on them …

13. How much of what we previously believed is true?
Why should this question concern us?
How should we address this concern?

14. Descartes' method
… and therefore that, once in a lifetime, everything should be completely overturned and I should begin again from the most basic foundations if I ever wished to establish anything firm and durable in the sciences. (Med. I, para. 1)

15. Descartes' method
Since Descartes is attempting to start again, he needs to establish some criterion by which to distinguish the beliefs that should be retained from those that should be jettisoned.

16. A decision-making method
Essentially first-person in nature. Why?
Because relying on beliefs about the external world or about other people would involve taking something for granted, something that legitimately could be called into question.
Must be reliable – it is no use if it admits of the possibility of further error.

17. A decision-making method

18. The goal Which beliefs should we seek to retain?
Easy answer: the beliefs that we want to retain are those beliefs that are true.
The problem is establishing the method by which we can identify the true beliefs.
Believing something to be true doesn't make it true, after all.

19. Example
I'm hard as nails

20. The method in Meditation I
To [overturn my beliefs] it is not necessary to show that they are all false – something I might never be able to accomplish! But since reason already convinces us that we should withhold assent just as carefully from whatever is not completely certain and indubitable as from what is clearly false, if I find some reason for doubt in each of my beliefs, that will be enough to reject all of them.

21. The method of doubt
Doubt is of essential importance to Descartes' method.
Rather than asking whether a belief is true or false and sorting them on this basis, Descartes asks whether a belief can be doubted:

22. The method of doubt
… reason already convinces us that we should withhold assent just as carefully from whatever is not completely certain and indubitable as from what is clearly false, if I find some reason for doubt in each of my beliefs, that will be enough to reject all of them.

23. Sensory doubt
Everything that I accepted as being most true up to now I acquired from the senses or through the senses. However, I have occasionally found that they deceive me, and it is prudent never to trust those who have deceived us, even once. (19)
If the senses have deceived us, we should not believe any claim that is based in sensory evidence.

24. Sensory errors Example of sensory error:
Perspective and distance errors
Mistaking a shadow for a person
Visual illusions

25. Sensory illusions

26. A new form of doubt
After discussing doubt from the senses and dreams, he introduces a form of doubt that is not based in familiar territory. It is not the sort of doubt that we engage with in daily life.
Rather, it is a form of suppositional, hyperbolic doubt:
Suppositional: it is based in a hypothetical scenario;
Hyperbolic: it is of exaggerated strength.

27. The evil genius
I will suppose that, not God who is the source of truth, but some evil mind, who is all powerful and cunning, has devoted all their energies to deceiving me. I will imagine that the sky, air, earth, colours, shapes, sounds and everything external to me are nothing more than the creatures of dreams by which an evil spirit entraps my credulity. I shall imagine myself as if I had no hands, no eyes, no flesh, no blood, no senses at all, but as if my beliefs in all these things were false. (22)

28. Modern variants

29. Descartes' view of experience
A note here on the way in which Descartes conceives of perceptual experience.
We usually conceive of perceptual experience to be of external objects and to essentially involve sense organs: the eyes, ears, etc.
On Descartes' view, one's experience could in principle be exactly the same even if one had no senses and there was no external world.

30. Descartes' view of experience
Experiences are private mental items; they exist in the mind of the subject and are distinct from physical objects, sense organs and even brain states. Qualitatively identical experiences could be brought about by radically different causes.
Experience as of a tree
/ \ could be caused by
An actual tree A deceiving demon

31. Indirect Realism
Causal relation
Resemblance relation

32. Demonic Reality

33. How to respond to scepticism
We can identify two response to scepticism:
1) Accept the sceptical position: we are not justified in claiming any knowledge;
2) Meet the sceptic's challenge: identify some certain truths that escape the sceptical doubt.
Descartes tries to take the second route.

34. The discovery of certainty
I convinced myself that there is nothing at all in the world, no sky, no earth, no minds, no bodies; is it not therefore also true that I do not exist? However, I certainly did exist,if I convinced myself of something. There is some unidentified deceiver, however, all powerful and cunning, who is dedicated to deceiving me constantly...

35. The discovery of certainty
… Therefore, it is indubitable that I also exist, if he deceives me. And let him deceive me as much as he wishes, he will still never bring it about that I am nothing as long as I think that I am something. Thus having weighed up everything adequately, it must finally be stated that this proposition 'I am, I exist' is necessarily true whenever it is stated by me or conceived in my mind. (23-4)
I am, I exist; that is certain (25)

36. (The latter features in the Discourse on Method)
What is the certainty?
I am, I exist Or
I think, therefore I am
(cogito, ergo sum)
(The latter features in the Discourse on Method)

37. Some initial questions
How do we arrive at this claim? Is it supposed to be:
(a) Self-evident,
(b) Supported by an argument, or
(c) Something else?

38. Some initial questions
What is the certain proposition supposed to be?
Is it ‘I exist’ or is it ‘I think’ or is it the cogito ‘I think, therefore I am’?
What is the connection between these?

39. What is it and how do we know?
The question of which claim Descartes makes is closely connected to the question of how we come to know it. Consider,
I think, therefore I am
This has the structure of an argument:
P1) I think
Therefore,
C1) I am

40. What is it and how do we know?
This looks like an invalid argument. There is nothing so far to connect thought to existence.
A further premise is required:
P1) I think
P2) Whatever thinks, exists
Therefore,
C1) I exist
Is this what Descartes intended?
If so, what justifies P2?

41. Whatever thinks, exists
But: if this is what Descartes intended, why is it unique?
Where’s the difference between ‘I think’ and ‘I walk’, ‘I eat’, etc? Would the same argument not work just as well with under such a substitution?
Aren’t arguments just as vulnerable to the doubt as arithmetic? Couldn’t we take a wrong inferential step and be prevented from noticing?
Alternative claim: ‘I think’ has a special status.

42. ‘I think’
That one is thinking is not in doubt – cannot be in doubt, given the essentially first person singular nature of the project.
(‘I walk’, ‘I eat’, etc., can be doubted.)
Even if someone says, ‘I think, therefore I am or I exist’, they do not deduce existence from thinking by using a syllogism, but they recognise it by means of a simple mental insight as something that is self-evident. (Replies to Second Objections)

43. ‘I exist’
So, on this reading that ‘I exist’ follows from the awareness of thinking is self-evident and does not require an argument of the sort discussed earlier.
As soon as one thinks, one is immediately aware of one’s own existence.
So, ‘I exist’ is the certain truth on this approach.

44. 'I exist'
Possibly: the act of thinking 'I exist' guarantees one's existence; it guarantees its own truth.
Consider:
It must finally be stated that this proposition 'I am, I exist' is necessarily true whenever it is stated by me or conceived in my mind'
So, experience isn't needed for this knowledge. (Contrast 'I walk' and 'I eat')

45. What am I?
I shall imagine that I am not the collection of limbs that is called a human body, nor some subtle air that is infused into those limbs … for I have supposed that those things do not exist. That supposition stands but, nonetheless, I am still something. (25)

46. What I am
It is thought. This alone cannot be detached from me. I am, I exist; that is certain. But for how long? As long as I think, for it might possibly happen if I ceased completely to think that I would thereby cease to exist at all. I do not accept anything at present that is not necessarily true. I am, therefore, precisely only a thinking thing, that is, a mind, soul, intellect or reason. (25) Notice: a metaphysical conclusion.

47. Physical things
Descartes accepts that it generally seems to us that we know the nature of physical objects better than we know the nature of the mind – hence the issue between 1), 2) and 3).
This is a troubling thought (27):
It really is surprising that I understand more distinctly things which I realize are doubtful, unknown and foreign to me than what is true, what is known and, ultimately, what is myself.

48. The wax example
The worry is that sensory experience or the imagination can reveal to us the true nature of physical objects more readily than we can come to grasp our own true natures.

49. The wax example

50. The wax
For example, let us take this wax. It has just been extracted from the honeycomb. It has not yet completely lost the taste of honey and it still retains some of the scent of the flowers from which it was collected. Its colour, shape and size are obvious. It is hard, cold, easy to touch and, if tapped with a finger, it emits a sound. Thus it has everything that seems to be required for a body to be known as distinctly as possible. (27)

51. How well do we know the wax?
Contrast the information we can give about the nature of the wax with the information we could uncover about the nature of the self: it seemed exceptionally difficult to give an account of the nature of the self, whereas the nature of the wax appears easy to state.

52. Is that really the case?
But notice that, as I speak, it is moved closer to the fire. It loses what remains of is taste, its smell is lost, the colour changes, it loses its shape, increases in size, becomes a liquid, becomes hot and can barely be touched. Nor does it still emit a sound if tapped. But does the same wax not remain? It must be agreed that it does; no one denies that, no one thinks otherwise. (27)

53. The new wax

54. So what? What is the point of this discussion?
The meditator claims that what was understood distinctly was not acquired through the senses or the imagination; these only revealed accidental, changeable or non-essential characteristics of the wax.
That it can change cannot be its true nature: every physical thing admits of such change.

55. An inspection of the mind
I have to concede, then, that I cannot in any way imagine what this wax is, but that I can perceive it only with my mind. What, then, is this wax that can be perceived only by the mind? It is the same wax I see, touch, imagine...
But what should be noticed is that perceiving it is not a case of seeing, touching or imagining, … but it is an inspection of the mind alone. (28)

56. Against empiricism Note that this is a direct attack on empiricism.
Contrast with this from of Meditation I:
Everything that I accepted as being most true up to now I acquired from the senses or through the senses. However, I have occasionally found that they deceive me, and it is prudent never to trust those who have deceived us, even once. (19)
Disingenuous – Descartes was never an empiricist.