1. Indirect Realism
Understand the argument put forward by the indirect realist.
Explain how a indirect realist would respond to perceptual problems.
‘Does the stance of indirect Realism improve the problematic position of Direct Realism?’

2. Direct Realism recap Explain to your partner What is Direct Realism?
What are the problems with Direct Realism?

4. Indirect Realism
Indirect realism claims that we perceive physical objects which are mind-independent, but we do so via, or in virtue of, perceiving mind-dependent sense-data that are caused by and represent physical objects. We perceive sense-data immediately, and physical objects indirectly.

5. To put that into English…
Indirect Realism (IDR) is a realist theory of perception: at least some of what we perceive is a feature of the external world and exists independently of our mind. However it is different to DR as IDR argues we indirectly perceive mind-independent physical objects through the medium of sense data. Ultimately IDR argues that there is something between the perceiver and the thing perceived.

6. We directly perceive sense data
Key term:
Sense data - what we are immediately aware of in perception i.e. the colour and shape of the desk as I see it now. (The mental representation)
Therefore:
We directly perceive sense data
And we indirectly perceive the mind-independent physical object causing the sense-data
In other words…..Our perception of reality is mediated by sense data, so that we must infer the existence and nature of the external world on the basis of the way it is represented to us in the mind.

8. Primary and Secondary Qualities
The distinction between primary and secondary qualities is important in understanding IDR as a realist theory of perception because it enables the IDR to claim that the external world really does exist independently of our minds. How? Well, this distinction explains sense data and thus can explain the differences in perceptual variation, the experience of illusions and hallucinations and the concept of a time-lag without jeopardising the existence of mind-independent physical objects.

9. Primary and Secondary Qualities
What are they?
What are their Characteristics?

10. Primary and Secondary Qualities
Primary qualities:
Qualities that exists independently of our perceiving them. In simpler terms, it refers to properties like shape, size and motion, that don’t depend on our senses.
Secondary qualities:
Qualities that require a perceiving mind to perceive them i.e. experience of the senses. In simpler terms, it refers to properties like colour, smell and taste that do depend on our senses.

11. Primary Qualities
Secondary Qualities
Explain how physical objects interact with each other.
Explain how physical objects interact with us.
Can be described precisely and mathematically.
Can’t be described with this precision.
Are ascribed to objects by science.
Are not ascribed to objects by science.
Are (arguably) essential to physical objects.
Are (arguably) not essential to physical objects.
Exist independently of the perceiver, in the objects themselves.
(Arguably) Exist only in the mind of the perceiver and not in the objects themselves.

12. Descartes on P+S Qualities
‘And although in approaching fire I feel heat, and in approaching it a little too near I even feel pain, there is at the same time no reason in this which could persuade me that there is in the fire something resembling this heat any more than there is in it something resembling the pain; all that I have any reason to believe from this is, that there is something in it, whatever it may be, which excites in me these sensations of heat or of pain.’
Descartes – Meditation 6

13. Descartes on P+S Qualities
Using the example of fire, Descartes argues that there is a distinction between the primary and secondary qualities of a mind-independent object. He argues that the sensation of heat within a perceiver cannot accurately resemble any real property of the fire. Why? Well, Descartes points out that we do not assume that the pain the fire may cause us is part of the fire itself. Therefore the ability to feel heat from a fire comes under the same line of logic: the heat the fire causes in us (just like the pain) is also not in fire.

15. Locke’s View
A ‘quality’ is a power that a physical property has to produce an idea in our minds.
Primary qualities are qualities that are inseparable from the subject whatever changes it undergoes. ‘The object has these properties “in and of itself”.’
For Locke they are:
Extension (occupies space no matter what the condition).
Shape
Motion
Number
Solidity (the quality of a physical object whereby it takes up space and excludes other physical objects from occupying exactly the same space).

16. Locke’s View
*Be aware that later on in his work Locke adds texture, size and situation to this list and leaves out number, extension and solidity.
He argued that these are all primary qualities – they are inseparable from the physical object – because physical objects must always ‘have some size and shape, they must always be at rest or in motion of some kind, they can be counted.’
Locke uses the example of dividing up a grain of wheat to help explain:

17. Locke’s View
‘Qualities thus considered in bodies are, first, such as are utterly inseparable from the body, in what state soever it be….e.g. take a grain of wheat, divide it into two parts; each part has still solidity, extension, figure, and mobility: divide it again, and it retains still the same qualities; and so divide it on, till the parts become insensible; they must retain still each of them all those qualities.’
Locke, Essay, II.viii.9

18. Locke’s View
Therefore no matter how many times we cut up and divide the grain of wheat up, the primary qualities will remain. The yellow colour of the grain of wheat will vary, change and disappear but its extension etc will remain.
Secondary qualities are not qualities of the physical object itself, but exist only in the act of perception. They come into existence through the effect of a physical object on a perceiver:

19. Locke’s View
‘…such qualities which in truth are nothing in the objects themselves, but powers to produce various sensations in us by their primary qualities, i.e. by bulk, figure texture, and motion of their insensible parts, as colours, sounds, tastes etc. these I call secondary qualities.’
Locke, Essay, II, viii.10

20. Locke’s View
The distinction is similar to the relationship between a word and the idea that the word ‘invokes’ in our mind i.e. we say the word football – we know the word doesn’t resemble the mind-independent object (the football) but it is arbitrarily associated with it. In simpler terms we call a football a football without analysing or really thinking about it being a football because our prior knowledge of the world around us tells us it is a football.  So too can we use this logic to explain how the white colour of a football doesn’t resemble the quality of the football which produces it. For this reason, we cannot directly know what it is that causes us to see white. Therefore it would appear that objects physically possess some qualities, whereas other properties are related to the minds perceiving them.
Qualities of objects that cause certain sensations in us (secondary) have something to do with the minute particles from which they are composed of and their movements (primary).

21. Leibniz on Secondary Qualities
Nothing happens without a reason.
‘…to make an arbitrary decision on how to link the sensation with the secondary quality is not God’s way’.
There must be a resemblance between our sensations and what has caused them.
Leibniz believes that instead our sensations are compounds of smaller and unperceived sensations or ‘minute perceptions’.
The sound of the sea is not a simple sense datum, but is compounded out of smaller perceptions which lie below the threshold of consciousness.
Since our sensations of secondary qualities are complex not simple, there is no reason to suppose that there is not some relationship of resemblance between them and secondary qualities.
It is just that we cannot bring this resemblance to consciousness in the way we can with primary qualities.

22. Final thoughts
Indirect realism is more than able to accommodate this primary secondary qualities distinction.
Imagine yourself reduced to the size of a molecule of air inside some minute ship that helps you get around the world. IMAGINE observing someone smell a smell or hear a noise. Nothing in what you observe would b e smelly or noisy or colourful. The molecules producing these experiences wouldn’t have these properties.
The world would be colourless and dull, but it would enable you to see how invisible parts compose physical objects and how these produce a reaction in human organisms.
Indirect Realism is the preferred view of most modern philosophers!