Representative Realism:Seems to be a distinction between appearance and reality.We perceive sense-data directly but the real world indirectly.Two worlds exist: the material world as it is in itself and the world as it appears to me.
Sense data:Subjective - the perceptual bridge between our minds and the independent physical object.Dependent on the perceiver rather than on the objects in the external world. They exist in our minds and exist as they are perceived. Sense data ceases to exist when we stop perceiving them.
Russell example of the table. When you view a table what you are directly aware of is not the physical independently existing table but a series of sense data. These sense data change as you perceive the table, change your position, touch the table, etc.
Sense data cannot be subjected to doubt - they are infallible - whereas objects are fallible. I can doubt what the physical apple looks like, I can doubt whether it exists at all because I am not perceiving it directly. However I know that I am perceiving sense data - I cannot doubt that I am perceiving something, whether there is a physical object behind the sense data or not.
In this way objects are public, available to everyone, while sense data are private, only available to our individual minds.
Since we can discuss the objects of sense data this would suggest that while we can doubt the object there does seem to be some type of object that the sense data relate to.
One analogy of the relationship between sense data and the objects they represent is in terms of a map. A map (the sense data) represents the land (the physical object) in various ways, e.g. the contour lines tell us the height and undulation of the land, symbols indicate physical features etc. From the map we can get a reasonable impression of the area represented without going there.
Time-lag argument:Existence of a time-lag between an event occurring and our perception of it demonstrates that we are perceiving sense data rather than the object itself.Representatives realists would argue that even if the sun ceased to exist we would still see it shining for eight more minutes. Therefore what we are seeing when we look at the sun must be sense data because the physical, independent object might no longer be there.
E.g. The sun's light takes eight minutes to reach the earth and therefore when we look at the sun and its light we do not see it as it is at that moment but as it was eight minutes ago.
Primary Qualities:- the qualities that belong to the object itself-essential nature of the object-independent of a perceiver-shape, size, weight - qualities that are measurable -these qualities generate the secondary qualities in our perception
Secondary Qualities:- the qualities that are found in our perception of an object-not intrinsic to the object-need a perceiver in order to exist-colour, smell, sound, taste-generated in our mind by the primary qualities that we see-dependent on circumstance
Science!:Scientists tell us that colours, smells and sounds don't exist in the world and that what really exists are light waves, chemicals, air waves, etc. which can be described in geometric and mathematical terms.
Problems of the 'Two World' View:
Resemblance: Our sense experiences are resemblances of the primary qualities as they do characterise the physical object of the external world however our sense data does not resemble any quality in the object. Berkeley argued that we could never compare our experience of shape and size with the real shape and size of an object. We can only ever be acquainted with our own experiences. Therefore RR does not actually tell us what the world is like. Without some independent means of being able to view both our sense impressions and the world, we cannot tell how accurate our mental representation of the world is.
Problem of Solidity:Locke argued that solidity was a primary quality. At any point in time an object's solidity is a given.
However physicists argue that objects are not necessarily solid, they can be broken down into particles and bundles of energy and because of this we have to question whether the idea of relative solidity makes any sense.Therefore the table cannot possess the primary quality of solidity, since if I change my perception and view the table at a quantum level, I can see that it has no solidity.
Inseparability: Berkeley argued that primary and secondary qualities are inseparable from primary ones- if an object does not have on then it does not have the other.For example, colour and shape are inseparable. If you draw a shape colour automatically fills the shape. I cannot imagine shape without colour as shape is purely the boundary of a colour.
The raw physical world is inaccessible to our senses - there is a 'veil of perception' between us and the world.
Problem of Variability: Supposedly primary qualities such as shape and size are arguably no less variable than sound or colour. Therefore the object must be denied of all qualities in the real world, not just secondary ones.
Problem of Causality:If all we know is our experiences, we cannot know whether our experiences resemble the objects themselves or whether the objects cause the experiences.
If we argue that A causes B then we must be able to experience both A and B in order to prove that a causal relationship exists.However we only have access to B - our sense data.
RR can therefore overcome the problems of NDR including perspective, changes in colour and time-lags whilst still accepting there is a physical world which contains independently existing objects.
Support for RR
Criticisms of RR