1. Recap – Indirect Realism Basics
Whiteboards: Summarise indirect realism in 20 words or less and illustrate with a picture.
Immediate objects of perception are mind-dependent sense data that are caused by / represent mind-independent objects / the external world.

2. Homework Check Time!
Using the green pen, sentence steal from other peoples work on your table whilst I come round to check homework!
What are primary qualities?
What are secondary qualities?
Why do philosophers distinguish between the two?
Give at least 2 examples for each.
Extension: Do you think Locke (and other philosophers) are right to make this distinction?

3. What are primary qualities?
Homework Recap
What are primary qualities?

4. What are secondary qualities?
Homework Recap
What are secondary qualities?

5. Why do philosophers distinguish between the two?
Homework Recap
Why do philosophers distinguish between the two?

6. Homework Check Time!
Do you think Locke (and other philosophers) are right to make this distinction?

7. Primary And Secondary Qualities
Lesson Objectives:
To analyse the theory of indirect realism (and in particularly primary and secondary qualities) in more detail.

8. P + S Qualities – Key Points
Things you should know so far:
Many of the arguments against direct realism hinge on the idea that some of the properties we perceive, do not exist in the objects themselves – but depend on a mind being present (secondary qualities).
Other properties are thought to have a real existence independent of our minds (primary qualities).
Philosophers (and indeed scientists) often draw this distinction because there are some properties that can differ from perceiver to perceiver and it seems obvious are not an inherent part of the object – that is to say whilst they may be caused by some part of the object, they are not in the object itself.

9. Example: Smell
This means by extension that humans that do not have the correct receptors in their noses (or damaged ones) cannot pick up certain smells, and animals / machines with more or better receptors can pick up more or enhanced odours.
This is consistent with current scientific thought on the subject as well.
The most popular theory about how the human sense of smell works is to do with the shape of molecules. Different smells are caused by different shapes of molecules interacting with the receptors in our nasal passageways. The molecules themselves do not smell, they’re not covered in some smelly property that we somehow perceive – they merely have a shape which in humans causes the subjective experience of a particular smell. Smell is therefore a secondary property – it is not an inherent part of the molecule but is caused by it.

10. Primary Vs Secondary
Consider Russell’s table: What properties can you list that are primary (i.e. part of the object) and what properties can you list that are secondary?
Primary Qualities
Secondary Qualities

11. Primary Vs Secondary NOT AN EXHAUSTIVE LIST!
Consider Russell’s table: What properties can you list that are primary (i.e. part of the object) and what properties can you list that are secondary?
Primary Qualities
Position (Where it is)
Number (How many)
Shape
Size
Motion (How fast / direction it is moving)
Secondary Qualities
Colour
Temperature
Sound
Beauty
Value
Taste
Addictive
Smell
NOT AN EXHAUSTIVE LIST!

12. P v S – Easy Way to Remember
If you’re struggling to tell the difference between / think you’ll struggle to remember the difference between Primary and Secondary Qualities the easiest thing to do is to consider what properties an object would have if no perceivers were around.
If a property would be there with no-one perceiving the object (i.e. size or shape) then it is primary.
If a property would be there only due to a perceiver (i.e. sound or colour) then it is secondary.

13. Pause for Thought – Whiteboards!
How would a direct realist and an indirect realist answer the old question of:
If a tree falls in a forest, and no-one is there to hear it, does it make a sound?

14. The Philosopher Bit - Locke
Those qualities are commonly thought to be the same in those bodies as those ideas are in us, the one the perfect resemblance of the other, and it would by most men be judged very extravagant if one should say otherwise. And yet he that will consider that the same fire that, at one distance produces in us the sensation of warmth, does, at a nearer approach, produce in us the far different sensation of pain, ought to bethink himself what reason he has to say — that this idea of warmth, which was produced in him by the fire, is actually in the fire; and his idea of pain, which the same fire produced in him the same way, is not in the fire. Why are whiteness and coldness in snow, and pain not, when it produces the one and the other idea in us; and can do neither, but by the bulk, figure, number, and motion of its solid parts?
What is Locke saying here? (Read the easier version on page 440 to help you)

15. The Philosopher Bit - Locke
We may conceive that the ideas of secondary qualities are also produced, viz. by the operation of insensible particles on our senses. For, it being manifest that there are bodies and good store of bodies, each whereof are so small, that we cannot by any of our senses discover either their bulk, figure, or motion — as is evident in the particles of the air and water, and others extremely smaller than those; perhaps as much smaller than the particles of air and water, as the particles of air and water are smaller than peas or hail-stones; — let us suppose at present that the different motions and figures, bulk and number, of such particles, affecting the several organs of our senses, produce in us those different sensations which we have from the colours and smells of bodies. It being no more impossible to conceive that God should annex such ideas to such motions, with which they have no similitude, than that he should annex the idea of pain to the motion of a piece of steel dividing our flesh, with which that idea hath no resemblance.
What is Locke saying here? (Read the easier version on page 441 to help you)

16. Overall:
Indirect realism fits easily with the primary / secondary quality distinction. Some of those properties that we perceive to be in objects really are there, some are not. So the former are an accurate reflection of the way the world is in reality, and the latter of a kind of illusion.
This is not to say that secondary qualities aren’t useful, they tell us interesting facts about physical objects (for example the way they reflect light generating colour), that can in turn lead to other useful information (particular colours being dangerous etc.)
They also map onto real differences in primary qualities between objects (size and shape of molecules etc.) it’s just generally these differences are too small for us to detect outright so we perceive them as secondary qualities instead.

17. Other reasons for P v S distinction:
Read through the information on pages (1-4) and summarise the four reasons philosophers and scientists support the primary / secondary quality distinction.

19. Whiteboard Summary – Key Facts:
Primary qualities are properties of an object that exist in the object itself. They are measurable mathematically or geometrically, they are essential to the object and are accessible to more than one sense.
Secondary qualities are produced by an object due to it’s particular makeup / order of primary qualities and are mind-dependent. They are not present in the object itself and may differ from perceiver to perceiver.

20. Homework – Russell on IDR
Read through the text you’ve been given carefully.
Annotate / Write a couple of sentences for each paragraph highlighting the key point that Russell is making.
How does his explanation relate to what we’ve covered on primary / secondary qualities?

21. Lesson Summary Lesson Objectives:
To analyse the theory of indirect realism (and in particularly primary and secondary qualities) in more detail.