Perception

Perception

The process by which we become aware of the external world, through our senses.

Perception is also often referred to in philosophy as sense experience.

External world

for each individual, the external world is everything that exists outside that individual’s mind.

the external world consists of physical objects such as tables, mountains, trees, bodies etc.

Realist

if you are a realist about something, then you believe it exists independently of our minds

(what many people would refer to as “real” philosophers would call mind-independent)

Anti-realist

if you are an anti-realist about something, then you believe its existence is mind-dependent

Direct realism

the immediate objects of perception are mind-independent objects and their properties

Perceptual Variation

the fact that objects appear to have different properties when perceived in different conditions. (this can include angle, distance, movement etc)

Hallucinations

Direct realism makes the claim that the immediate objects of perception are mind independent objects and their properties.

P1. Hallucinations occur when a person perceives something which doesn't exist outside the mind

C1. So what they perceive, the hallucination, exists only in their mind.

P2. Hallucinations can be subjectively indistinguishable from veridical perceptions.

P3. But if hallucinations and veridical perceptions are subjectively indistinguishable, then the person must be aware of the same thing in both cases.

C2. So, from C1, P2 and P3, what they are directly aware of during veridical perception must also be in the mind.

C3. Hence we perceive the world indirectly and direct realism is false.

Time lag

Direct realism makes the claim that we perceive objects directly as they really are with all the properties we perceive them to have.

P1. The light from distant objects (such as the Sun) takes time to reach our eyes

C1. So what we are seeing now may no longer exist.

C2. So what we are seeing and what is there are different.

P2. This is no less true for physical objects at any distance.

C3. And so, what we directly see are appearances not physical objects and direct realism is false.

Indirect Realism (also called representative realism)

the immediate objects of perception are mind-dependent objects objects that are caused by and represent mind-independent objects.

Sense data

the immediate objects of perception. They are subjective, non-physical and mind-dependent, and supposedly provide us with knowledge of a mind-independent, physical world. For the indirect realist, sense-data are a representation or image of mind-independent objects in the external world.

Mind-dependent

subjective and relative to the perceiver. Determined by my experience of it.

Mind-independent

objective and not relative to the perceiver. Not determined by my experience of it

Transient

temporary, exist only when perceived

Permanent

constant, exist regardless of whether or not they are perceived

Private

accessible only to the perceiver

Public

accessible to all perceivers

Infallible

are not subject to doubt, I cannot doubt the existence of table-like sense data

Fallible

can be subjected to doubt. The object might not exist

Differences between sense data and physical objects

Sense data	Physical objects
Mind-dependent	Mind-independent
Transient	Permanent
Private	Public
Infallible	Fallible

indirect perception

• Perception of objects is mediated by sense data

• Sense data represent objects but they don't resemble objects