Introduction to Philosophy EXAM 1

Section 7.2 Facing Reality

Perception and the External World

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7.2-2

Direct Realism

o The doctrine that perception puts us in direct contact with reality.

o “Direct” because nothing comes between the world and our perception of it.

o “Realism” because there is an external world that is not affected by our thoughts.

7.2-3

The Argument from Illusion

1.  What we see is bent.

2.  The pencil is not bent.

3.  So what we see is not the pencil.

7.2-4

Sense Data

o Sense data are the objects that are immediately known in sensation, such as colors, sounds, smells, hardnesses, roughnesses, etc.

7.2-5

The Problem of the External World o We can’t compare our sense data with

the world; all we can do is get more sense data.

o So how can we know what the world is like in itself?

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Representative Realism

o The doctrine that sensations are caused by external objects and that our sensations represent those objects.

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Thought Probe: Hypothesizing the External World

o Locke: the hypothesis of an external world provides the best explanation of our sense data.

o Compare that hypothesis with the dream hypothesis. Which does better with regard to the criteria of adequacy: simplicity, scope, conservatism, and fruitfulness?

7.2-8

Primary vs. Secondary Qualities o  A primary quality is one possessed by material

objects such as: solidity, extension, figure, and mobility.

o  A secondary quality is one that exists in the mind but not in material objects themselves such as: heat, color, taste, etc.

o  According to Locke, sense data of primary qualities resemble the qualities of material objects.

7.2-9

Berkeley on Primary and Secondary Qualities o  Primary qualities such as figure and

extension are as variable as secondary qualities.

o  What looks round from one angle can look elliptical from another.

o  Consequently, they can’t be considered to resemble qualities of physical objects.

7.2-10

Thought Experiment: The Inconceivability of the Unconceived

o Material objects are supposed to exist even when no one is thinking about (conceiving of) them.

o But it’s impossible to conceive of something that exists unconceived. (Once you conceive of it, it’s no longer unconceived!)

o Thus the notion of a material object is self-contradictory.

7.2-11

Esse et Percipi: To Be is to Be Perceived o  Since one cannot

conceive of something existing unconceived, it’s impossible for something to exist unconceived.

o  Thus, everything that exists must be conceived by someone.

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God and Reality

o  If to be is to be perceived, then when we stop perceiving something it ceases to exist.

o  But God never stops perceiving anything.

o  So God holds things in existence by thinking about them.

7.2-13

Knox’s Limerick – Young Man’s Query There once was a young man who said “God

Must think it exceedingly odd If he finds that this tree Continues to be When there’s no one about in the quad.”

7.2-14

Knox’s Limerick – God’s reply

Dear Sir: Your astonishment’s odd I am always about in the quad And that’s why the tree Will continue to be Since observe by Yours faithfully, God

7.2-15

Phenomenalism

o Berkeley held that things are nothing but patterns of sensations.

o According to phenomenalism, all talk of things is reducible to talk of sensations.

o Objection: What we perceive depends on the state of our bodies, but the state of our bodies cannot be reduced to sensations.

7.2-16

Conceiving the Unconceived

o It is not possible to conceive of something that exists unconceived.

o But it is possible to conceive that something exists unconceived.

o Thus the notion of material objects is not self-contradictory.