Section 7.2 Facing Reality

1. Section 7.2Facing Reality Perception and the External World

2. Direct Realism • Direct Realism is the doctrine that perception puts us in direct contact with reality. • “Direct” because nothing comes between the world and our perception of it. • “Realism” because there is an external world that is not affected by our thoughts.

3. The Argument from Illusion • What we see is bent. • The pencil is not bent. • So what we see is not the pencil.

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

5. The Problem of the External World • We can’t compare our sense data with the world; all we can do is get more sense data. • So how can we know what the world is like in itself?

6. Representative Realism • Representative realism is the doctrine that sensations are caused by external objects and that our sensations represent those objects.

7. Thought Probe: Hypothesizing the External World • Locke believes that the hypothesis of an external world provides the best explanation of our sense data. • Compare that hypothesis with the dream hypothesis. Which does better with regard to the criteria of adequacy: simplicity, scope, conservatism, and fruitfulness?

8. Primary vs. Secondary Qualities • A primary quality is one possessed by material objects such as: solidity, extension, figure, and mobility. • A secondary quality is one that exists in the mind but not in material objects themselves such as: heat, color, taste, etc. • According to Locke, sense data of primary qualities resemble the qualities of material objects.

9. Berkeley on Primary and Secondary Qualities • Primary qualities such as figure and extension are as variable as secondary qualities. • What looks round from one angle can look elliptical from another. • Consequently, they can’t be considered to resemble qualities of physical objects.

10. Thought Experiment: The Inconceivability of the Unconceived • Material objects are supposed to exist even when no one is thinking about (conceiving of) them. • Berkeley claims that material objects cannot exist because it’s impossible to conceive of something that exists unconceived. (Once you conceive of it, it’s no longer unconceived!)

11. Esse et Percipi: To Be is to Be Perceived • Since one cannot conceive of something existing unconceived, Berkeley concludes that it’s impossible for something to exist unconceived. • Thus, everything that exists must be conceived by someone.

12. God and Reality • If to be is to be perceived, it would seem that when we stop perceiving something it ceases to exist. • But although we may stop perceiving something, God never stops perceiving anything. • So God holds things in existence by thinking about them.

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”

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

15. Phenomenalism • Berkeley held that things are nothing but patterns of sensations. • According to phenomenalism, all talk of things is reducible to talk of sensations. • Objection: What we perceive depends on the state of our bodies, but the state of our bodies cannot be reduced to sensations.

16. Conceiving the Unconceived • It is not possible to conceive of something that exists unconceived. • But it is possible to conceive that something exists unconceived. • Thus the notion of material objects is not self-contradictory.