The secondary quality argument for indirect realism

R1. When I look at a rose, I see something that is red.

R2. The red thing cannot be the rose itself (since redness is a secondary quality which exists in

the mind of the perceiver rather than the objects we perceive).

IC. So it must be a mental image of the rose – a sense datum.

C. But this means I see the rose indirectly, by seeing its sense-datum- in which case direct realism is false.

In a nutshell• Indirect realism, through primary & secondary qualities,

develops a ‘two-world’ view of perception.• World No. 1 = the world as it really is. Objects with

primary qualities obey the laws of physics here in a sense-less world i.e. no colour, taste or smell.

• But it is this world, in conjunction with our perceptual system, that causes us to perceive ‘World Number 2’.

• World No. 2, the world we directly perceive, is a representation of World No. 1, the world as it is.

Written task:Create an analogy to help explain the distinction between primary and secondary qualities and how it explains how we perceive the external world.

How convincing is this distinction?

• Is it really possible to imagine an object with no secondary qualities? Can you really imagine an orange as colourless, odourless and without texture?

Objections to indirect realism

Learning objectives:1. To understand the objection that indirect

realism causes scepticism about the existence of the external world

2. To begin to evaluate indirect realist replies to it

Problem 1: How can we know there is an external world?

• Indirect realists say that all we ever perceive is sense-data.

• Sense-data is mind-dependent.• So how can we know whether anything exists

beyond the mind?

Problem 1: How can we know there is an external world?

• See Russell ch. 2, last para. on page 8 (to half way down p.9)

Can you answer Problem 1 for indirect realists? How can we know there is an

external world, even though it is perceived via sense-data?

Can you answer Problem 1 for indirect realists? How can we know there is an

external world, even though it is perceived via sense-data?

• Similarity between different sense-data suggests it comes from one thing.

• It makes more sense to say there is a stimulus.• There are changes to physical matter when

we’re not perceiving it (e.g. decaying banana). Makes more sense to say it changed whilst not being perceived.

Russell’s first response

• Read the text from ch. 2, p.9 (2nd half)

Russell’s first response

• People perceive the same thing.

• What is his concern with this reason?

Russell’s preferred response

• Look at me.• Close your eyes• Look at me again.

• What’s the best explanation for our sense-data?

Physical objects existing or not existing?

Russell’s preferred response

• See last para. on p.10- half way down p.12

Russell’s preferred response

• Summary: Saying that there is an external world (including other minds) is the best hypothesis.

Locke’s two responses

Try not to think about a crocodile.

Locke’s two responses

See page 42 Lacewing.

Locke’s two responses

1) I can’t choose my sense-data.2) My sense-data gives me a coherent picture.

To what extent are Locke and Russell’s replies helpful in relieving us from

scepticism about the existence of the external world?

Read 42-43 of Lacewing and write a half page long answer to this question

Learning objectives

• To recap the distinction between primary and secondary qualities.

• To evaluate the extent to which the distinction answers the objection to indirect realism that it leads to scepticism about the nature of the external world.

Problem 2: How can we know the NATURE of the external world?

• Summary on your work sheet

Response 1: Locke on primary and secondary qualities

• Read through your sheet

Write down an example of a primary quality of the apple.

Write down an example of a secondary quality of the apple.

• How do you know the shape is a primary quality?

Would the apple still roll off the desk if no one was perceiving it?

What does this tell us about shape?

Would its colour still be having effects if no one was looking at it?

Evaluation of Locke’s distinction

• How clear is he?

• Do you agree there is such a distinction?

How does the distinction help defend indirect realism?

How does the distinction help defend indirect realism?

• The subjective view of secondary qualities can be used to defend indirect realism – we don’t perceive the world directly.

How does it answer problem 2?

Problem 2: Indirect realism leads to scepticism about the nature of the external world (what it is like).

How does answer problem 2?

• Primary qualities are accurate reflections of reality… so SOME of our perceptions represent the world.

• The world of appearances (of secondary qualities) is a representation of the world of reality (of primary qualities).

• What’s the difference between representing and resembling?

What would an indirect realist say?• If a tree falls over in a forest, and no one is

there to hear it…

…does it make a noise?

Use primary and secondary qualities in your answer.

Explain why for Locke, extension is a primary quality. (5 marks)

Learning objectives• To know Berkeley’s critique of the primary /

secondary quality distinction• To know Russell’s response to issue 2• To evaluate whether indirect realism does lead

to scepticism about the nature of the external world.

Summary

• Criticism: On indirect realism, how can you ever know the nature of the external world when all there is is sense-data?

• Reply: We do have a true resemblence of the world via our perception of primary qualities.

Bishop Berkeley (idealist)

• What does he say about the distinction between p and s qualities?

Extension of arg. from perceptual variation

• Different animals perceive time differently.• https://www.youtube.com/watch?v=Bc-YpWBxsHU

• How could this be used to reply to the indirect realist’s point about primary vs. secondary qualities?

Extension of arg. from perceptual variation

• Different distances affect our perception of shape and size.

5 Mark Question

• Explain why, for Berkeley, there cannot be a distinction between primary and secondary qualities.

• 10 minutes. (3/4 minutes planning time).• 5 A full, clear and precise explanation.

The student makes logical links between precisely identified points, with no significant redundancy.

4 A clear explanation, with logical links, but some imprecision, redundancy.3 The substantive content of the explanation is present and there is an

attempt at logical linking. But the explanation is not full and/or precise.

Russell’s response to problem 2

• Sense-data tells us relations btwn objects.

Russell’s response to problem 2

• Find 2 objects of the same colour in this room.

• Can we know that they are the SAME colour?

What’s your conclusion?

• If indirect realism is true, I think you can / can’t know the nature of the external world because…

Do we perceive the physical world directly?

Yes – perceive it directly No – perceived indirectly

Do we perceive the physical world directly?

Yes – perceive it directly• Replies from direct realism• Common-sense• How can something mental

represent something physical?

• Indirect realism results in scepticism.

• Berkeley: Yes – redefines ‘physical object’ as bundles of ideas.

No – perceived indirectly• Args against direct realism,

e.g. time-lagDemonstrate sense-data

• Distinction between primary and secondary properties shows that we do know the nature of the world, but not directly and not entirely representatively.