René Descartes (1596-1650)
René Descartes
René Descartes Method of doubt
René Descartes Method of doubt Things you believed that you now know to be false?
René Descartes Method of doubt Skeptical arguments (illusion, dreams) > doubt of senses
Possibility of Dreaming Descartes: In my sleep I experience the same things as madmen do when they are awake or sometimes even less probable things. How often have I been persuaded, in the quiet of the night, of familiar things that I was here in my robe sitting near the fire when in fact I was lying disrobed between the sheets!
Possibility of Dreaming Descartes: It certainly seems to me now that I am looking at this paper with waking eyes; that this head I move is not asleep; that I deliberately and knowingly extend my hand and feel it. What happens in sleep is not so distinct. No doubt! As if I do not remember being tricked while asleep by similar thoughts on other occasions!
Possibility of Dreaming Descartes: While I think about this more carefully, I see so plainly that there are no certain indications by which we may clearly distinguish being awake from being asleep that I am dumbfounded. And my astonishment almost persuades me that I am asleep.
Descartes s Contribution Evil deceiver
Possibility of an Evil Deceiver Imagine an all-powerful but evil being out to deceive me It makes my mind skip every time I think or draw a conclusion
Evil Deceiver Descartes: I shall therefore suppose not that God who is supremely good and the fountain of truth, but some evil genius of the greatest power and cunning, who has employed all his energies to deceive me.
Descartes s Contribution Evil deceiver > doubt of logic and mathematics
Classical Rationalism We are able to have knowledge of the world independently of experience because the structure of the mind matches the structure of the world
Philo of Alexandria Forms are ideas in the mind of God Our minds and the world are both stamped with the Word of God Word Word
Descartes What if our minds and the world are stamped with different stamps? Word Verbum
Descartes What if our minds and the world are stamped with different stamps? Word λογος
Descartes What if our minds and the world are stamped with different stamps? Word ϖ ð
Descartes What if our minds and the world are stamped with different stamps? Word
Plato s Philosophy of Mind The Good Participation Form Recollection This is a triangle Perception Object
Augustine s Philosophy of Mind God Participation This is a triangle Form Illumination Perception Object
Descartes s Philosophy of Mind God Why think they match? This is a triangle Innate Ideas Perception Object
Must I Doubt Everything? I suppose, then, that all the things that I see are false; I persuade myself that nothing has ever existed of all that my fallacious memory represents to me. I consider that I possess no senses; I imagine that body, figure, extension, movement and place are but the fictions of my mind. What, then, can be esteemed as true? Perhaps nothing at all, unless that there is nothing in the world that is certain.
Foundations Is there anything we can t doubt? Foundation for the rest of knowledge
I am But there is some deceiver or other, very powerful and very cunning, who ever employs his ingenuity in deceiving me. Then without doubt I exist also if he deceives me, and let him deceive me as much as he will, he can never cause me to be nothing so long as I think that I am something.
I am...we must come to the definite conclusion that this proposition: I am, I exist, is necessarily true each time that I pronounce it, or that I mentally conceive it...
I am (Sum) What makes I am special?
I am (Sum) What makes I am special? I can t think it without existing
I am (Sum) What makes I am special? I can t think it without existing I doubt whether I am? But if I doubt, I am
Foundations Is there anything we can t doubt? Foundation for the rest of knowledge I am
I think What of thinking? I find here that thought is an attribute that belongs to me; it alone cannot be separated from me.
I think to speak accurately I am not more than a thing which thinks, that is to say a mind or a soul, or an understanding, or a reason, which are terms whose significance was formerly unknown to me. I am, however, a real thing and really exist; but what thing? I have answered: a thing which thinks.
Cogito, Ergo Sum I think, I am True every time they are thought or uttered
I Think (Cogito) What makes I think special?
I Think (Cogito) What makes I think special? The thought I think is self-justifying It makes itself true
I Think (Cogito) What makes I think special? The thought I think is self-justifying It makes itself true I doubt whether I think? But doubting is thinking
Foundations Is there anything we can t doubt? Foundation for the rest of knowledge I think, I am
A Thing That Thinks But what then am I? A thing that thinks. What is a thing that thinks? It is a thing which doubts, understands, [conceives], affirms, denies, wills, refuses, that also imagines and feels.
Appearances Finally, I am the same who feels, that is to say, who perceives certain things, as by the organs of sense, since it truth I see light, I hear noise, I feel heat. But it will be said that these phenomena are false and that I am dreaming. Let it be so; still it is at least quite certain that it seems to me that I see light, that I hear noise and that I feel heat. That cannot be false; properly speaking it is what is in me called feeling; and used in this precise sense that is no other thing than thinking.
Conclusions I am a thing that thinks I am essentially a thing that thinks I can know my own mind more securely than I can know anything else: I see clearly that there is nothing that is easier for me to know than my mind.
Anything else? I am certain that I am a thinking being; but do I not therefore likewise know what is required to make me certain of something?
Transcendental Argument Argument concerning the conditions of the possibility of something A is possible But A could be possible only if B Therefore, B
Clear and Distinct Perceptions Certainly in this first knowledge there is nothing that assures me of its truth, excepting the clear and distinct perception of what I state, which would not indeed suffice to assure me that what I say is true, if it could ever happen that a thing that I conceived so clearly and distinctly could be false; and accordingly it seems to me that already I can establish as a general rule that all things that I perceive very clearly and very distinctly are true.
Descartes s Argument Argument concerning the conditions of the possibility of certainty It is possible for me to be certain of something But that could be possible only if I could trust what appears to me clearly and distinctly to be true Therefore, I can trust what appears to me clearly and distinctly to be true
Clarity and Distinctness But can I doubt the premises? Can I doubt the conclusion? Can I doubt whether it follows? Note the caution: seems (Latin: videor )