Foundations of Knowledge

Before asking how we justify claims of knowledge in different areas, we need to

consider what kind of thing we can base any knowledge on: there must be some basic pieces of knowledge that we are completely justified in

accepting, without having proven or even argued that they are true; and then there must be means to arrive at further knowledge from

those basic pieces of knowledge.

Foundations of KnowledgeFor each of the following propositions it has

been claimed that our knowledge of it is incorrigible, i.e. that we could not possibly be mistaken about these matters. Try to think of situations where such a belief might be wrong.

I see something red in front of me.

John does not have a female brother.

For basic knowledge to be incorrigible, as we require, it is not enough for the belief to be infallible (i.e. knowledge implies truth,) it must also be irresistable (i.e. truth implies knowledge.)

Foundations of KnowledgeThere are very few propositions which

cannot possibly be wrong just because someone believes them – and certainly not enough of them to serve as a basis of all our knowledge.

We must therefore be content to accept the evidence of our senses and memory as basic knowledge, provided that there are no overriding considerations to the contrary.

Sense Experience & Perception

Human beings are usually said to have 5 senses.

1. List the usual 5 senses and their sense organs, and make further subdivisions if appropriate.

2. Try to decide on an order of the 5 senses, according to how essential they are for our functioning in the world.

3. Decide on an order of the 5 senses according to how much information they provide us with.

4. Are there any other senses that you think should be included?

Sense Experience & Perception

A common distinction, first made by John Locke (1632-1704,) is that between the primary qualities of objects, which are inseparable from them no matter what state they may be in, and their secondary qualities, which "are nothing in the objects themselves, but the powers to produce the various sensations in us by their primary qualities" (An Essay Concerning Human Understanding, 1690, II.)

So primary qualities are really in the objects, whereas secondary qualities, as perceived sensations, are only in the observer. This led Locke to argue that some of our ideas give us genuine information about the reality 'out there,' (and hence knowledge,) while others do not.

Sense Experience & Perception

According to Locke's distinction, which of the following are primary and which are secondary qualities?

a. solidity

b. taste

c. extension

d. odour

e. number

f. figure

g. colour

h. sound

What arguments do you think there are for and against there being ESP?

It might be thought, then, that our immediate perceptions are such that they give us certain knowledge, and that they can therefore serve as the basis of other knowledge.

However, the example of the Necker cube shows that perception is an active process of interpreting the information we receive through our senses and of making sense of it. In general, when we look at something, we are unconsciously 'guessing' or forming hypotheses about what we can see. Most of the time we don't realise this, because there isn't any problem. But with the Necker cube, there are two equally likely hypotheses which we can hold, so we 'flip' between the two.

What arguments do you think there are for and against there being ESP?

It might be thought, then, that our immediate perceptions are such that they give us certain knowledge, and that they can therefore serve as the basis of other knowledge.

However, the example of the Necker cube shows that perception is an active process of interpreting the information we receive through our senses and of making sense of it. In general, when we look at something, we are unconsciously 'guessing' or forming hypotheses about what we can see. Most of the time we don't realise this, because there isn't any problem. But with the Necker cube, there are two equally likely hypotheses which we can hold, so we 'flip' between the two.

What arguments do you think there are for and against there being ESP?

"Perception is not determined simply by stimulus patterns; rather it is a dynamic searching for the best interpretation of the available data ... perception involves going beyond the immediately given evidence of the senses" (Gregory, 1966.)

Perception is "the process of assembling sensations into a useable mental representation of the world;" it "creates faces, melodies, works of art, illusions etc. out of the raw material of sensation" (Coon, 1983.)

Since perception, then, is a process which not simply records sense data but selects from them, draws inferences from them and organises them, it is a process which can go wrong.

What arguments do you think there are for and against there being ESP? Look at the optical illusions below and discuss how they

may arise. What, here, are the "overriding considerations to the contrary" why we do not accept the evidence of our senses?

The Müller-Lyer illusion.

The Ponzo illusion

The horizontal-vertical illusion

Gestalt Theory An account of some ways in which our perceptions are

automatically organised is given by Gestalt theory (from Ger. Gestalt, figure, shape,) which says that we tend to perceive things as wholes which are more than the sums of the given parts. Amongst the principles according to which our experience is organised are the following:

1. Figure/ground: even a man who gained his sight at age 47, after having been blind since birth, immediately had figure/ground-perception, even though other things he had to slowly learn.

2. Similarity and proximity: other things being equal, we group together things that are near each other, and similar things.

3. Closure, continuity and symmetry: we tend to organise what we perceive into simple, complete wholes.

Gestalt TheoryDiscuss the

following perceptual situations in terms of the above three Gestalt principles.

In the diagram on the left, can you see two different crosses in the square?

Gestalt TheoryIn the diagram on

the right, do you see the first figure as the two parts shown, or as a triangle and a horizontal line?

Gestalt TheoryConsider the two strings of letters on

the right. How do you immediately parse the letters in each of the strings, into two groups or into three?

Size ConstancySize constancy refers to the fact that our

perceptions of the size of objects are relatively constant despite the fact that the size of objects on the retina vary greatly with distance. These pages show some demonstrations of the power of size constancy using a photograph I have. Take a look at the photograph to the right and see if all the people in it all look reasonably the same size.

Especially compare the near and far people in the photograph.

Size Constancy

Size ConstancyNow look at this version of the

photograph. All I did was cut out the figure in the background and paste him further forward. The figures are exactly the same size. Measure them! This photograph represents a variation of a classic demonstration of the power of size constancy done by Boring (1964).

Size Constancy

Perception

Two of the most powerful and effective of all human fears are the fear of failure and the fear of success.

PerceptionPerception is affected by various extraneous factors as

well, such as context and other situational variables (the 'perceptual set,') and motivation and emotion.

The principle of perceptual accentuation/sensitisation, is where things that are relevant or salient for us are perceived as larger, brighter, more attractive.

Now, the kinds of errors and distortions described above can affect not only our perception of the physical world, but also the beliefs on which we base our judgments.

This is something we must bear in mind when we make claims to knowledge, and when we critically assess such claims.

Perception - ActivitiesTry to give examples of how ...

1. a person's attitude, such as a racial prejudice or a preference for a make of car, might be based on some of the above errors and distortions.

2. I may think I know something, when in fact my belief is wrong and is based on some mistaken or distorted perception.

The Nature-Nurture Debate

In philosophy there are two schools of thought: rationalists such as Plato (427-347 B.C.) have held that our knowledge is based upon certain innate principles, which are "stamped upon the mind of man;" whereas empiricists such as John Locke have believed that at birth our minds are like a blank sheet of paper (a tabula rasa) and that all knowledge is empirical, i.e. based on sense experience of the outside world.

In various areas of psychology, too, the question whether, or to what extent, certain of our abilities or characteristics are innate (hereditary) or whether they are acquired (i.e. due to the environment) has been hotly debated. In some cases the question is open to empirical investigation.

The Nature-Nurture Debate

Read the following summaries of experiments and decide whether they support the 'nativist' or the empiricist position.

1.

size of cube [cm] 30 30 90 90

distance [m] 1 3 1 3

head-turns [%] 98 58 54 22

2- to 3-months old babies were taught to turn their head at the sight of a 30 cm cube at a distance of 1 m. When the stimulus was varied, the following results were obtained, showing the extent to which the babies generalised their response (Bower, 1966):

The Nature-Nurture Debate

Three chimps were reared, from birth until they were 7 months, under different conditions, and their visual abilities tested (Riesen.)

Debi, who had spent the whole time in darkness, had suffered retinal damage, but neither of the other two had.

Kova, who had spent 1-2 hours a day exposed to diffuse or unpatterned light by wearing translucent goggles and had spent the rest of the time in darkness, was noticeably retarded: receiving two electric shocks a day from a yellow and black striped disc, she needed six days of training before she even whimpered when the disc was shown, and she was very slow to follow a moving object just with her eyes.

Lad, who had been raised under normal lighting conditions, was no different from any other normally-reared chimp.