Meditation I:

Concerning Those Things That Can Be Called into Doubt

What is knowledge?

Background

Descartes (1596 - 1650) began work on the Meditations in 1639 and they were published in 1641. The official title is Meditations on First Philosophy, in which the existence of God and the immortality of the soul are demonstrated - though some believe that there was a printer error and that it should actually read immateriality of the soul.

The book is made up of six meditations and it is written as if one meditation occurred per day. The aim of the book was built on the premise that something is knowledge only if it cannot be doubted (a position known as infallibilism) and therefore, he wanted to discard any beliefs which were not beyond doubt and then see what can truly be ‘known’. Along with his other works, Discourse on Method and Principles of Philosophy, it outlines his conception of knowledge and Science, the new Mechanical Philosophy. It laid the foundations, the framework for many of our discussions today - namely the nature of science, the nature of reason, and the nature of the mind.

In the first meditation, Descartes outlines his sceptical method - and the thought experiment which shall identify all those beliefs which must be discarded.

The three waves of doubt

If I have a reason to doubt x (am not certain of x) then I do not know x. [infallibilism/Philosophical scepticism]
The measure of truth (the source of certainty) can be found either in:
- Reason
- Experience (through the senses)
(First wave of doubt): My senses have deceived me in the past, so they might be deceiving me again.
- (However, they only deceive me when I do not use them properly. So, this is not a reason to doubt everything.)
(Second Wave of doubt): It is possible that I am asleep, so I cannot trust what I perceive.
- (However, dreams are not logical, yet my experience is logical. I can remember going to sleep. So, this is not a reason to doubt everything.)
(Third Wave of doubt) If I am being deceived by an evil deceiver, then all the information that comes from my senses is false. All external things might be illusions.
- (I cannot rule this possibility out)
∴ I am not certain of any knowledge that I have gained from my senses
∴ if I can know anything, the source must be reason [Rationalism]

I shall then suppose, not that God who is supremely good and the fountain of truth, but some evil genius not less powerful than deceitful, has employed his whole energies in deceiving me; I shall consider that the heavens, the earth, colours, figures, sound, and all other external things are nought but the illusions and dreams of which this genius has availed himself in order to lay traps for my credulity; I shall consider myself as having no hands, no eyes, no flesh, no blood, nor any senses, yet falsely believing myself to possess all these things; I shall remain obstinately attached to this idea, and if by this means it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power [i.e. suspend my judgement], and with firm purpose avoid giving credence to any false thing, or being imposed upon by this arch deceiver, however powerful and deceptive he may be.

–Meditation I

Discussion

Firstly, Descartes seems to think that we can only know things which cannot be doubted. Is this correct? Is this what the word know means? Think about when it would actually make sense to say, 'I know I have hands'.

Secondly, Descartes seems to be arguing that everything he is sensing could be illusory, but can that idea make any sense? Normally, we would judge something to be an illusion precisely because it conflicts with our sensory experience. If I claimed to have a private jet, you might only believe me if you saw it. But here Descartes has flipped the meaning. Now it is our sensory experience which is doubtable - so how are we to judge what an illusion is?

Is it ok that he changes the meaning of words in this way? Would it be ok if someone said, 'this triangle had four sides', or 'this stick has no length'?

Tasks

How did Descartes define knowledge and what was his method for distinguishing between knowledge and that which we only think is knowledge?
Give one objection to Descartes' approach.
Do you find Descartes' thesis convincing?

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