Questions for Discussion!

Questions for Discussion! • Do you agree with Henry that Jack doesn’t know that his battery is dead? • Do you agree with Henry about his general principle (“In general, you can’t know…”)? • Regardless of whether you agree with him, did Henry kind of get on your nerves? • Did you sort of want to slap him around a little bit?

Guiding Question What can we know?

Metaphysics Metaphysics is the study of the nature of reality. (The study of how things really are) Some metaphysical questions: • Do tables and chairs exist? • Does god exist? If so, what is he/she/it really like? • What is the nature of the self? • Do we have free will?

Epistemology The study of the nature of knowledge. Some epistemological questions: • What is knowledge? • Does anyone know anything at all? • What does it take for a belief to be justified?

SEVERAL years have now elapsed since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation, if I desired to establish a firm and abiding superstructure in the sciences… To-day, then,… I will at length apply myself earnestly and freely to the general overthrow of all my former opinions. -Descartes, Meditation One

Descartes’ 3-Step Method 1.Tear down all of his beliefs. 2.Find sturdy foundations. 3.Build back up. (“establish a firm and abiding superstructure in the sciences”).

But, to this end, it will not be necessary for me to show that the whole of these are false--a point, perhaps, which I shall never reach; but as even now my reason convinces me that I ought not the less carefully to withhold belief from what is not entirely certain and indubitable, than from what is manifestly false, it will be sufficient to justify the rejection of the whole if I shall find in each some ground for doubt. Nor for this purpose will it be necessary even to deal with each belief individually, which would be truly an endless labor; but, as the removal from below of the foundation necessarily involves the downfall of the whole edifice, I will at once approach the criticism of the principles on which all my former beliefs rested. -Descartes, Meditation One

Descartes’ Goal Descartes wants to achieve certainty in all of his beliefs. (He wants to construct a belief system that is completely immune from error.)

Descartes’ 3-Step Method 1.Tear down all of his beliefs. (Doubt everything that can be doubted.) 2.Find sturdy foundations. (Find those beliefs which are certain and indubitable.) 3.Build back up. (Infer other beliefs from the "foundational" beliefs.)

General Principle for Knowledge? • Descartes quest for certainty has often been read as a view about the requirements for knowledge. • On this view, knowledge requires certainty. • I’ll refer to this view as Descartes’ “Rule-Out” Principle for knowledge: If you can't rule-out every possibility on which X is false, then you do not know that X is true. • Or, to put it a slightly different way:

All that I have, up to this moment, accepted as possessed of the highest truth and certainty, I received either from or through the senses. I observed, however, that these sometimes misled us; and it is the part of prudence not to place absolute confidence in that by which we have even once been deceived. -Descartes, Meditation One

Deception Argument Premise 1 The senses sometimes deceive us. -------------------------------------------------------- Conclusion So for all we know, they always deceive us.

…How often have I dreamt that I was in these familiar circumstances, that I was dressed, and occupied this place by the fire, when I was lying undressed in bed? At the present moment, however, I certainly look upon this paper with eyes wide awake; the head which I now move is not asleep; I extend this hand consciously and with express purpose, and I perceive it; the occurrences in sleep are not so distinct as all this. But I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming. -Descartes, Meditation One

The Dreaming Argument P1:I cannot rule out the possibility that I am merely dreaming that there is a cup on the table in front of me (because “there exist no certain marks by which the state of waking can ever be distinguished from sleep”). P2:If I cannot rule out this possibility, then I do not know that there is a cup on the table in front of me. (The “rule-out principle”.) -------------------------------------------------------------- C:Therefore, I do not know that there is a cup on the table in front of me.

The Evil Demon Argument P1:I cannot rule out the possibility that an evil demon is deceiving me into thinking that there is a cup on the table in front of me. P2:If I cannot rule out this possibility, then I do not know that there is a cup on the table in front of me. (The “rule-out principle”.) -------------------------------------------------------------- C:Therefore, I do not know that there is a cup on the table in front of me.

Questions for Discussion!