indirect realism

indirect realism is

mind-independent objects exist and we perceive them but via sense-data which is caused by and represents physical objects

three key properties of sense data

mental, only exist when perceived, private

argument for indirect realism

we perceive many things not caused by physical objects, something must cause this perception, that is sense-data, indistinguishable from other perceptions, always sense-data

what is a quality, according to locke

the power a physical objects has to produce an idea in our mind

what are primary qualities

utterly inseparable, properties of the object in and of itself

what are the primary qualities

extension, shape, motion, number, solidity

what are secondary qualities

qualities objects have that are nothing but powers to produce various sensations in us

what do objects have whether perceived or not

primary qualities

issue posed for indirect realists about reality → scepticism about physical objects

if all we perceive is sense-data, how do we know what produces the sense-data

what statement does scepticism about physical objects lead us to

if indirect realism is true, we cannot know that it is true

Russell’s first argument to solve issue of scepticism

sense data is private, so no two people ever perceive the same thing unless they are indirectly perceiving the same physical object. people have very similar sense-data when looking at the same thing. best explanation is that a physical object is causing their sense data. so physical objects exist

issue for russell’s first argument against scepticism of physical objects

it relies on other people existing, but if physical objects don’t exist that means other people also don’t exist (begging the question)

Russsell’s second argument against scepticism of physical objects

either physical objects exist and cause my sense data, or they do not exist and do not cause my sense data. i cannot prove either claim is true. thus, i have to treat both as hypotheses. the hypothesis that physical objects exist and cause my sense data is better. thus, physical objects exist.

way of defending the argument that ‘it is a better hypothesis to say physical objects exist and cause my sense data than do not exist’

if there is a cat in the corner of the room, then a cat on the sofa, it makes more sense that the cat has moved than that it just spring into existence in my mind

Locke’s argument from involuntary experience defending indirect realism

we cannot avoid experiencing sense data whereas we have control over memories or imagination e.g. by stopping imagining

Trotter Cockburn’s argument defending indirect realism

some objects produce multiple sense-data and we can infer one from the other e.g. train moving closer = increasing noise

Locke’s second argument defending indirect realsim (weaker than cockburn’s)

i can change how paper looks by writing on it. I can plan what I will write, but to watch the paper actually change I have to write

if physical objects don’t exist, we cannot explain

why sense-data aren’t under our control, why we should get the same info from different senses, why we can infer what will happen in one sense from another and the complex interaction between our actions and our senses

whats another way of interpreting how sense-data works, countering the objection about physical objects only being a hypothesis and thus not good enough

sense-data is how we perceive things rather than something which gets between us and the real world

indirect realism says that sense-data is not only caused by physical objects, it …

represents them

example outlining the scepticism about the physical nature of objects

if all you knew was smoke, would you be able to work out fire was the cause

berkely’s objection about sense-data representing physical objects

sense-data is perpetually fleeting and variable cannot represent something fixed and constant

example to outline berkely’s objection to sense-data representing physical objects

a plate looks like a different shape to us from different angles, but only has one actual shape

what do indirect realists reply to berkely’s objection about the nature of physical objects

sense-data represents physical objects, causal relations are very detailed and systematic