One Argument for Distinguishing Primary and Second
Locke's representative realism
Indiscernability of identicals- X and Y are only the same object if they have the same qualities
Primary qualities are OBJECTIVE
Secondary qualities are SUBJECTIVE
If we disagree about a primary quality we can resolve it by some shared standard but secondary qualities are not subject to such checking. We simply have to agree to disagree.
Illustrate- agree about the weight of the steak but not about its taste!
Arguments For Sense Data
I perceive something which has differences from the object in the external world. If my perception has different qualities from object in external world it cannot BE the object in the external world. Epistemic gap.
I perceive object with quality X. No relevant entity in the external world HAS quality X so I am not perceiving an entity in the external world. I am perceiving a mental representation of the object
Person X and person Y both look at object O. Person X perceives it to have quality A and person Y perceives it to have quality B. O cannot have both quality A and quality B so what they are perceiving is not O but their sense data.
Three Characteristics of Sense Data
Sense data exists in the mind of the perceiver and only there.
Has exactly the qualities perceived and no others. Sense data has no hidden depths
Sense data subject to variation unlike objects in external world eg shape of coin
Representative Realism- relation to external world
There IS an external world which CAUSES my perceptions which resemble but are not identical with the external world
Sceptical arguments- epistemic gap
Veil of perception,