Jim Fahey Department of Cognitive Science 9/16/2010 Neo’s Escape: Plato’s Cave, Descartes’ Evil Genius, Berkeley & The Matrix Jim Fahey Department of Cognitive Science 9/16/2010

What’s Real? Plato’s Republic, Bk VII: The Cave - There are prisoners “in chains” so that they can come to perceive only that which is “projected” before them on “the wall of the cave;” What would they believe to be the nature of the real if this is all that they encounter in their life time?

What’s Real? The Cave (cont.) - In fact, however, the cave is a complicated world. Behind the shackled prisoners is a low wall and just beyond that a road running close to the wall with beings marching up and down carrying all sorts of things on sticks as one would carry a banner in a parade. Light is cast on the “banners” by a fire that stands close to the road and the result is that the paraded “banners” cast shadows on the walls that the prisoners must face.

What’s Real? The Cave (cont.) - But there is light from another source as well. The mouth of the cave, while a long way up, opens to the light of stars, moon and sun. Indeed the very energy of the cave and all of its contents seems powered by the light from without.

What’s Real? Escape from the Cave – Suppose that a prisoner escaped from his chains. Likely it would take him some time to adjust to his new view of the world. Indeed, at first, he would not believe what he experienced. Moreover, as he ascended through the cave he would at first most likely be blinded by the light he perceived. Only after some time would he be able to gaze steadily at first the fire, then the stars, moon, and finally the sun.

What’s Real? Escape from the Cave (cont.) Would a prisoner who escaped from the Cave ever choose to return? Plato thinks not … But? …Cypher?

What’s Real? Freeing the other prisoners? What would be the likely response if the escaped prisoner were to return to his/her neighbors and report that what they take to be reality is not reality at all?

What’s Real? But what is this “reality” to which Plato alludes? Answer: the world of Forms; But what’s that? Consider the case of two chairs … Plato argues they both must participate in (exemplify) CHAIRNESS!

What’s Real? (Aside about Knowledge) How do we come to know about “chairness” and the “world of forms?” Plato thinks that true knowledge is knowledge of the world of forms and that the only avenue to true knowledge is our faculty of reason. There is no sensory knowledge of physical objects since Physical Objects are mere shadows of the forms they exemplify and “knowledge of shadows” is not knowledge at all.

FINDING A FOUNDATION for HUMAN KNOWLEDGE DESCARTES’ DREAM FINDING A FOUNDATION for HUMAN KNOWLEDGE

Goal: KNOWLEDGE THAT IS A. CERTAIN (INDUBITABLE); B: ABOUT TRULY EXISTING THINGS.

Method: CARTESIAN DOUBT Descartes’ search for KNOWLEDGE involves a kind of “process of elimination.” He examines the kinds of BELIEFS he might claim to know and considers whether it is possible for him to DOUBT those beliefs. If it is possible, then Descartes does not KNOW them. If he finds a BELIEF THAT IS IMPOSSIBLE TO DOUBT, then this would count as KNOWLEDGE and could serve as a FOUNDATION for other claims to know.

Cartesian Doubt: The Process CATEGORIES OF BELIEF 1. Beliefs about “distant” things WHY DUBITABLE? Senses/memory ARE FALLIBLE

Cartesian Doubt: The Process CATEGORIES OF BELIEF 2. Beliefs based on “present sensing” WHY DUBITABLE? I might be dreaming

More on the “Dream Possibility” Descartes believes that even if he were dreaming, this would not render dubitable his beliefs about: A. Simple Mathematical Truths B. Beliefs that there are things such as extension through space (SHAPE) and time (DURATION) Or, in other words, THAT THERE ARE PERSISTING MATERIAL OBJECTS IN GENERAL.

Cartesian Doubt: The Process (cont.) CATEGORIES OF BELIEF 3. Beliefs about: A. Simple Math B. That there are Material Objects in general WHY DUBITABLE? EVIL DECEIVER

Cartesian Doubt: The Process (One More Try) CATEGORIES OF BELIEF COGITO ERGO SUM I AM THINKING THEREFORE I EXIST!!!! WHY DUBITABLE? INDUBITABLE!!!

Berkeley’s Master Argument

Descartes’ View of Perception

Components of Berkeley’s (simplified) Argument P: everyday, common sense, “physical objects” A: things that I am directly aware of by means of my senses I: ideas M: things that DO NOT exist independent of MIND (i.e., things that are mind dependent)

Berkeley’s Master Argument All P are A All A are I All I are M ------------- All P are M

Berkeley’s Master Argument But if ALL EVERYDAY, COMMON SENSE, “PHYSICAL OBJECTS” ARE THINGS THAT DO NOT EXIST INDEPENDENT OF MIND THEN WHAT IS THE CAUSE OF WHAT WE PERCEIVE?

Berkeley’s Idealism (Ideaism)

Berkeley’s Idealism (Ideaism) And thus, on Berkeley’s view, all “physical objects” are complexes of ideas that depend for their existence on the mind of God and, moreover, our human ideas of “physical objects” ultimately derive from ideas placed in our respective minds by God!

Neo’s Escape: Plato’s Cave, Descartes’ Evil Genius, Berkeley & The Matrix SO while watching the Matrix you should ask yourself WHAT IS REAL? and HOW DO I KNOW? Moreover, how would you compare (contrast) the world of the Matrix with the worldviews of Plato, Descartes (and his Evil Genius), and Berkeley?