sense datum

In the the philosophy of perception, the theory of sense data was a popular view held the early twentieth century by philosophers such as Bertrand Russell, C. D. Broad, H. H. Price, A.J. Ayer and G.E. Moore, among others. Sense data are supposedly mind-dependent objects that we are aware of in perception, whose existence and properties are known directly to us, and about which we cannot be mistaken. Sense data are supposed represent 'real' objects in the world outside the mind, about whose existence and properties we often can be mistaken.

The nature of sense data

According to the theory, sense data appear to us exactly as they are. For example, when we twist a coin it 'appears' to us as elliptical. This elliptical 'appearance' cannot be identical with the coin (for the coin is perfectly round), and is therefore a sense datum, which somehow represents the round coin to us. Another example is the reflection which appears to us in a mirror. There is nothing corresponding to the reflection in the work external to the mind (for our reflection appears to us as the image of a human being apparently located inside a wall, or a wardrobe). The appearance is therefore a mental object, a sense datum.

The idea that our percepts are based on sense data is supported by a number of arguments. The first is popularly known as the Argument From Illusion. ^[1] From a subjective experience of perceiving something, it is theoretically impossible to distinguish perceiving something which exists independently of oneself from an hallucination or mirage. Thus, we do not have any direct access to the outside world that allows us to distinguish it from an illusion based on identical sense data.

Sense data theories have been criticised by philosophers such as J.L. Austin and Wilfrid Sellars and more recently by Kevin O'Regan and Alva Noë. Much of the early criticism may arise from a claim about sense data that was held by philosophers such as AJ Ayer. This was that sense data really do have the properties they appear to have. Thus, in this account of sense data, the sense data that are responsible for the experience of a red tomato really "are red". In one sense this is ridiculous, since there is nothing red in a brain to act as a sense datum. However, in another sense it is perfectly consistent - in the sense that the data "are red" if experienced directly, even if they are not if they are experienced in a contrived and inappropriately indirect way by looking at someone's brain. Certainly, the tomato itself is not red except in the eyes of a red-seeing being. Thus when we say something 'is red' there is a false assumption that things can have appearances without reference to that to which they appear - as implicit in the sense data theory. Thus the criticism that sense data cannot really be red is made from a position of presupposition inconsistent with a theory of sense data - so it is bound to seem to make the theory seem wrong. More recent opposition to the existence of sense data appear to be simply regression to naïve realism.

References

External links

• Sense Data - an article by Michael Huemer in the Stanford Encyclopedia of Philosophy.

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