INDIRECT REALISM(Our experience of the external world is indirect and mediated by

subjective mental representations i.e. sense-data)

Indirect Realism (also called representative realism)

The immediate objects of perception are mind-dependent objects that are caused by and represent mind-independent objects.

Key features: Addresses some of the criticisms of direct realism whilst at the

same time preserving some of its strengths. Contrary to direct realism, the immediate objects of perception

are not physical objects but sense data. For example, deception occurs when sense data do not match

up with the object, hallucinations occur when sense data occur in the mind but there is nothing corresponding to them in the world and with variability of perception, it is our sense data which change not the object.

However, the common sense view that objects exist independently of perception is retained.

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Sense Data (pl.) Sense Datum (s.)

Sense data are the immediate objects of perception. They are subjective, non-physical and mind-dependent, and supposedly provide us with knowledge of a mind-independent, physical world.

Sense data are the subjective, mind-dependent intermediaries of perception that supposedly provide us with knowledge of a mind-independent, physical world. They are the empirical atoms of colour, sound, smell, taste and texture out of which experience is composed.

Thus, on this account, when I view an object such as Russell’s table, what I am directly aware of is a series of sense data which give rise to my perception of the table. These data vary as my perspective changes in the manner that Russell outlines in the quote we considered earlier. A sense datum, as opposed to the table itself, depends for its existence upon my perceiving it; it exists, unlike the table itself, exactly as I perceive it, and when I cease perceiving it, it ceases to be.

We can distinguish between sense data and objects as shown in the table below:

Sense data ObjectsMind dependent (mental), subjective and relative to the perceiver. Determined by my experience of it

Mind independent (physical), objective and not relative to the perceiver. Not determined by my experience of it

Transient, exist only when perceived

Permanent, exist regardless of whether or not they are perceived

Private, accessible only to the perceiver

Public, accessible to all perceivers

Infallible, are not subject to doubt. I cannot doubt the existence of table-like sense data

Fallible, can be subjected to doubt. The table might not exist

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Sense data and the external world

According to indirect realism, sense data mediate between the perceiver and the external world. While the real table is distinct from sense data relating to it, the sense data all represent the table in some way. Furthermore, while the sense data are private, the fact that we can have meaningful discussions about the objects of the sense data (we could both count the legs on the table and come to agreement) seems to imply that the sense data do relate to a real public object somehow. Again, the fact that we could sit at the table playing cards until the sun goes down and it is too dark to see implies that the object in question is permanent.

So, sense data represent objects to me but there is no guarantee that they are identical with the objects in question. Rather, the relationship could be thought of as being like a map to a territory: reading a map can tell us things about the territory that it represents without necessarily resembling it.

Similarly, sense data allow us to infer the existence of the objects they supposedly represent and, in so doing, make a further inference as to the existence of an external world.

The crucial point to understand here is that the sense data theorist is in no way claiming that the perception of sense data proves the existence of an external world. Rather, the external world has the status of a working hypothesis which seems the best fit for the facts as we know them. For Russell, the existence of the external world is the most economic and systematic hypothesis for explaining the occurrence of the sense data.

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Science-inspired arguments for sense data (NB: arguments from illusion and variability of perception can also be used to support the existence of sense data)

When we look at what science tells us about the world, we seem to run into problems for the direct realist which are then exploited by the indirect realists to argue in favour of sense data.

The argument from physics (the table)

Physics tells us that Russell’s apparently solid table is actually not solid at all, but rather a lattice of energy. Clearly if we accept the physicists’ account, then what direct realism asserts is wrong: reality as is and reality as perceived are two separate things. Were direct realism correct in its assumptions, i.e. were we to apprehend reality directly, then it would follow that the objects of our experience would present themselves to us as lattices of energy and not, as is the case, the colourful objects of experience.

Time-lag arguments (the sun)

Time-lag arguments draw our attention to the time difference between an event’s occurrence and our subsequent experience of it, claiming that if an object ceases to exist but a time-lag occurs so that we continue to view it as existing, then we cannot be directly viewing that object. This example from Russell should clarify things:

“It takes eight minutes for the sun’s light to reach us; thus, when we see the sun we are seeing the sun of eight minutes ago. So far as our sense data afford evidence as to the physical sun they afford evidence as to the physical sun of eight minutes ago; if the physical sun had ceased to exist within the last eight minutes, that would make no difference to the sense data we call ‘seeing the sun’. This affords a fresh illustration of the necessity of distinguishing between sense data and physical objects.”

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However, both arguments above start from the premise that there is an external world in order to promote the argument for sense data and so cannot then use sense data to cast doubt upon that world, by claiming that the world is a hypothesis that we can never know.

ISSUES WITH INDIRECT REALISM/SENSE DATA

Sense-data theories arguably generate more questions than they manage to answer, e.g. the ontological question concerning where they exist, and sceptical questions concerning how we can know whether our representations are accurate and how we can know that sense data are representations in the first place.

Problem 1: Leads to scepticism about the existence of the external world (attacking ‘realism’)

In separating the world as it appears from the world as it really is, indirect realism has made this latter world seemingly inaccessible to our senses. A veil of perception has dropped down between us and the world, meaning that we only ever have access to our representations and cannot peer beyond the veil to see the world as it really is.

This generates scepticism about the external world, with claims that our present sensations could be caused by something entirely different – a dream, a powerful demon, a virtual reality machine or

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by being a brain in a vat. Now, even if these possibilities are far-fetched, the very fact that they are conceivable shows that we have no way of verifying that it is in fact the real world we are perceiving. Such doubts will always be possible so long as there remains a gap between the world we perceive and the world as it is. So even if, as above, we try to infer the existence of a material world by the fact that we are alive, such an inference can always be called into question; for we could still be making such an inference if there were no such world.

Russell’s Response: External world is the ‘best hypothesis’

“… every principle of simplicity urges us to adopt the natural view, that there really are objects other than ourselves and our sense-data which have an existence not dependent upon our perceiving them…Since this belief does not lead to any difficulties, but on the contrary tends to simplify and systematize our account of our experiences, there seems no good reason for rejecting it. We may therefore admit that the external world does really exist, and is not wholly dependent for its existence upon our continuing to perceive it.”

Locke’s Responses:Coherence of the various senses

We could doubt whether our sense data from one sense was caused by a physical object in the external world. But if this experience is supported by sense data from other senses, it seems more likely that the various forms of sense data are caused by a real physical object:

“If you see a fire, you may doubt whether it is anything but a mere fancy; but then you can feel it too, and be convinced by putting your hand into it. Your hand

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certainly could never be given such agonizing pain by a mere idea or imagined fancy, unless the pain is a fancy too!”Lack of choice over our experiences

In addition, we can’t choose which sense data we experience. If there were no physical objects causing the sense data, we might be able to change it, to choose not to experience it, or to experience it differently. But we can’t do these things, which suggests that our sense data are not caused by us, but by a separate external world.

“When my eyes are shut, I can choose to recall to my mind the ideas of light or the sun that former sensations have lodged in my memory, or choose to set such ideas aside and instead take into my ·imaginative· view the idea of the smell of a rose or the taste of sugar. But if at noon I turn my eyes towards the sun, I can’t avoid the ideas that the light or sun then produces in me.”

Problem 2: Leads to scepticism about the nature of the external world (attacking ‘representative’)

If, as the name of the theory suggests, what we perceive is a kind of representation of the world, how do we know how accurate that representation is? In other words, how can we be sure that the human perception of the world in any way resembles the world as it is? If the existence of physical objects is just inferred from our sense data, how can we be sure they are accurate in their representation? We cannot place our sense data and the physical objects side by side in order to make a comparison. In other words, we can’t get out of our own minds and adopt a God’s-eye view, as it were, from which to observe both our sense data and the world. But without such a point of view we cannot establish when we are being deceived or how accurate our representations are.

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Russell’s Response:Sense data tell us of ‘relations’ between objects

Russell acknowledges that sense data cannot acquaint us with every aspect of physical objects. But they can tell us for certain about the ‘relations’ between objects:

“If one object looks blue and another red, we may reasonably presume that there is some corresponding difference between the physical objects; if two objects both look blue, we may presume a corresponding similarity. But we cannot hope to be acquainted directly with the quality in the physical object which makes it look blue or red.”

Locke’s Response: The distinction between primary and secondary qualities

One way to respond to this problem is to claim that sense data can give us accurate information about some properties of objects, but not all of them. That is, some properties of objects are mind-dependent and some are mind-independent:

The primary and secondary properties thesis

So, sense-data theory fails because it is dependent upon the separation of world and perception in such a manner that all we can know is sense data and not the world itself. However, objects must have some properties that are real otherwise they wouldn’t exist. Also, science takes the ‘real world’ and our ability to investigate it as a given. Perhaps objects indeed possess certain properties but other properties are more subjective in that they rely on a mind being present, i.e. some of the properties we perceive in objects really are there, and some are not. So, the former are accurate reflections of the way the world is in reality and should form the basis of our knowledge of the world, while the latter are not ‘truly real’.

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It is here that science may be able to help us by providing evidence in support of the thesis of primary and secondary qualities originally put forward by Locke.

Primary and secondary qualities are not always defined or divided up in precisely the same way by philosophers. But a traditional division is set out in the table below:

Primary qualities - real, physical qualities which exist in the object itself

Secondary qualities - do not exist within the object itself but are caused within us by the primary qualities of the object

Position (i.e. where the object is)

Number (i.e. how many there are)

Shape Size (i.e. how big it is) Motion (i.e. how fast it is

moving)

Colour Heat and cold Smell Sound Taste

Three ways of distinguishing primary from secondary qualities.

1. Primary qualities physically exist in the objects themselves, and are inseparable from the objects and essential to them. Imagine an apple devoid of any shape, size, position or motion, either still or moving. Here, it seems imagination fails us. An object cannot lack these properties and remain an object. They are the qualities which an object actually has, regardless of the conditions under which it is being perceived, or of whether it is being perceived at all.

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Secondary qualities do not physically exist in the objects themselves, are separable from the objects and not essential to them. Think, again, of an apple. If you imagine it making no sound then you are still thinking of an object. So, making a noise cannot be an essential property of an object like an apple. Similarly, imagine it to have no taste, or colour. Still, you are thinking of an object, albeit not a very appetising one. And so on for other secondary properties. An object can lack these properties and remain an object. Secondary qualities are the ‘powers’ that the objects have to produce certain sensations in the mind and are the ways things have of appearing to us.

2. Primary qualities are measurable, they lend themselves readily to mathematical or geometric description; secondary qualities do not. The positions of any objects relative to any others can be precisely described, as can their number, shape, speed and so forth. So for example, I can say that one object is twice as big, moving three times as fast as another etc. However, subjectively experienced smells, colours and so on just don’t behave like this. Cheese and onion flavour could never be twice salt and vinegar, I can’t weigh the taste of coffee etc. We can’t add, subtract, divide or multiply tastes, flavours, colours, touches or smells in the same way that we can sizes, shapes, speeds, masses and quantities. So it seems that secondary qualities are less amenable to being represented mathematically.

3. Physical objects act and interact with one another purely on the basis of their primary qualities. Secondary qualities have nothing to do with how objects behave.

The outcome of a collision between two moving objects, say billiard balls, depends on

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their mass, direction of movement, speed, and how they are held together by the atoms that compose them. In other words, the outcome depends entirely on the primary qualities of the objects involved.

Secondary qualities are just the powers of an object to produce experiences in perceivers. This cannot have an effect on how physical objects interact with each other.

So, there are reasons to suggest that we should hold some sort of primary/secondary quality distinction, and it appears we must make a distinction between how the world appears to us and how it really is.

A strength of the primary/secondary quality thesis is that it manages to encompass:

The common-sense view that there is an external world independent of perception

The sense-data theorist’s representative view, bolstered by science, that the world may not be as we perceive it and that there are qualities of sensation that are dependent upon us rather than the object.

It manages this by avoiding the claim that the two are mutually exclusive, but rather combining them. This is an attractive option because it allows us to give a sophisticated account of perception that seems to gel with our experience of it.

Take the falling tree example, we can see how the primary/secondary quality thesis will allow us to say that there is no sound (secondary quality) if there is nobody to hear it fall, without having to doubt that the solid object that is the tree actually falls (primary qualities).

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Problems arising from the view that mind-dependent objects represent mind-independent objects:

Remember that Locke used the distinction between primary and secondary qualities to show that we can have knowledge of the external world. Berkeley argues that in fact there are no primary qualities, and that all our perceptions are of secondary qualities.

Earlier we suggested that one way of determining whether a quality was primary as opposed to secondary was to see if we can conceive of the object without that quality. We gave the example of an apple and suggested that it could be imagined without any colour, smell, taste, sound, and so on (secondary qualities) but not without its shape, size, position or motion (primary qualities).

However, Berkeley argues that it is a mistake to think that we can perceive of an apple which has no secondary qualities. We were deluding ourselves when we tried to imagine an odourless, colourless apple (e.g. we probably imagined a white apple).

If an object can only be conceived of with both primary and secondary qualities then our ideas of secondary qualities are inseparable from the primary. So if we accept that our perceptions of secondary qualities exist only in the mind, then our perceptions of primary qualities must be in the mind too. In which case, none of the mind-dependent objects of our perception accurately represent mind-independent objects, and we return to the problem that indirect realism leads to scepticism about the nature of the external world.Problems arising from the view that mind-dependent objects are caused by mind-independent objects (the ‘linking’ problem):

Berkeley raises an additional problem with the idea that our sense-data could be caused by objects that are entirely independent of

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the mind. How can something physical and mind-independent cause an idea in the mind? How could nerve signals in the brain produce sensations of sound and colour? Berkeley poses this as an objection to realism, and 300 years later, the problem remains unsolved.

Berkeley concludes that Indirect Realism fails to deal with the problem of scepticism about the existence and nature of the external world, and he proposes an alternative theory: that the mind-dependent objects of our perception are the objects themselves; so that all material objects depend on minds for their existence. This theory is called Idealism.

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