perception as a source of knowledge

direct realism (5 m)

• immediate objects of perception = mind-independent objects and their properties

• two elements - perceiver and object perceived

• no mediator - perceived immediately and directly

• senses detect properties (e.g. colour, shape) - inherent in objects themselves

• object and properties continue to exist when unperceived

sense data (3 m)

• content of perceptual experience

• private - exists in mind of an individual

• caused by/represents mind-independent objects

argument from perceptual variation (5 m)

• appearance of physical objects varies depending on conditions

• russell (problems of philosophy) - table appears white where light reflects but brown otherwise - apparent shape changes when viewed from different angles

• possible for our perception to vary without changes to properties of the object itself

• apparent properties are not the same as real properties - so dr is false

• immediate objects = sense data - used to infer existence of objects

dr response to perceptual variation (5 m)

• relational properties - vary in relation to something else

• e.g. being to the left or right of something is a real property - but is dependent on position of the objects and of the perceiver

• russell’s table - has the property of appearing kite-shaped relative to certain perceivers

• rps belong to the object and are directly and immediately perceived - even though they can change

• therefore not necessary to introduce sense data as a mediator - objects are still directly perceived

argument from illusion (5 m)

• objects can appear to have particular properties that they do not - e.g. a straight straw appears bent when placed in glass of water

• perceiver is directly aware of this apparent property - a bent-looking straw

• object does not have this property in reality - real straw is not bent

• what the perceiver is directly aware of (bent straw) and what is real (straight straw) are distinct

• therefore we do not perceive objects directly - so dr is false

dr response to illusion (5 m)

• i am not directly aware of anything distinct from the physical object - appearance of the straw is not a thing in itself

• i am directly aware of the real straw - but it appears bent because of the circumstances (light travelling through two different mediums)

• i am directly and accurately perceiving the refraction of light as it travels through the glass of water

• drs do not have to assume that objects appear exactly as they are

• can appear differently because of how they relate to the perceiver - not necessary to introduce sense data as mediator

argument from hallucination (5 m)

• hallucination = i perceive something that exists only in my mind - mind-dependent sense data

• can be subjectively indistinguishable from veridical perceptions

• if this is the case i must be aware of the same thing in both cases

• so what i am directly aware of during veridical perception must also be in the mind - sense data/ideas

• therefore we perceive the world indirectly - so dr is false

response to hallucination (5 m)

• hallucinations and veridical perception being subjectively indistinguishable does not mean they are the same phenomenon in reality

• vp caused by physical object impacting on sense organs

• hallucinations caused by some malfunction in the brain

• they can be indistinguishable to the perceiver - still distinct phenomena

• hallucinations occur in mind - does not follow that vp involves a purely mental element (sense data)

time-lag argument (5 m)

• russell (problems of philosophy) - light from sun takes 8 mins to travel to earth

• not seeing the sun as it is now but as it was 8 mins ago - could have ceased to exist in last 8 mins but would not know yet

• if what you are perceiving may no longer exist, you cannot be perceiving it directly - must be sense data caused by sun’s light impacting on sense organs

• true of distant objects - also true of close objects - time-lag is just far shorter

• we are directly aware of appearances/sense data and not objects themselves - so dr is false