realism

Direct realism

Is the theory that we perceive things through the world directly. As mind independent objects and their properties are the immediate objects of perception (veridical)

Indirect realism

-Is the theory that we perceive things of the world through sensations.

• It claims that physical objects are never the immediate objects of perception and we do not perceive them directly but rather through sense-data .

Idealism

It is the claim that the world is not real and we perceive sensations and not physical objects. That there is no mind-independent reality.

Perceptual variation

P1) That the way an object looks to us depends on many different factors C1) So, the properties that I perceive immediately vary depending on different factors. P2) The real, mind-independent properties of an ob- ject do not vary. C2) Therefore the properties I perceive immediately are not the real, mind-independent properties of objects. P3) Direct realism claims that mind-independent ob- jects and their properties are the immediate objects of perception. C3) So Direct realism is false.

Argument against perceptual variation

The direct realist can respond by appealing to the concept of a relational property. Definition: A relational property is a mind-independent property that an object has due to its relation to other objects, for example, "London is north of Paris." Appearances can be understood as relational properties. The way an object appears depends on its relation to the observer, and on environmental conditions. Thus, relational properties (appearances) of objects are the immediate objects of perception, and because they are mind-independent, direct realism can explain perceptual variation this way.

Illusions

P1) In illusions objects appear to have properties that they do not have in reality. C1) So, in illusions, the properties that I perceive im mediately are not the real, mind-independent prop- erties of the object. C2) Therefore the properties I perceive immediately are not always the real, mind-independent proper- ties of objects. P2) Direct realism claims that mind-independent ob jects and their properties are the immediate objects of perception. C3) So Direct realism is false.

Argument against illusions

The direct realist can respond by appealing to the concept of a relational property. Definition: A relational property is a mind-independent property that an object has due to its relation to other objects, for example, "London is north of Paris." Appearances can be understood as relational properties. The way an object appears depends on its relation to the observer, and on environmental conditions. Thus, relational properties (appearances) of objects are the immediate objects of perception, and because they are mind-independent, direct realism can explain illusions this way.

Hallucinations

P1) In hallucinations people perceive objects that do not exist in reality. C1) So, in hallucinations, the objects that I perceive immediately are not real, mind-independent objects. C2) Therefore the objects I perceive immediately are not always real, mind-independent objects. P2) Direct realism claims that mind-independent ob- jects and their properties are the immediate objects of perception. C3) So Direct realism is false.

Argument against hallucinations

The direct realist can respond by defend- ing the disjunctive theory of perception.

The disjunctive theory of perception claims that hallucinations are not an ex- ample of perception at all. Rather they are closer to imagination, where sensations are generated from within the individual.

So, the direct realist claims that when I experience an object, either I am perceiv- ing it (directly) or I am hallucinating . This means that hallucinations are not a valid counter-example to the direct realist's theory of perception.

Time delay

P1) In many or all examples of perception there is a time-delay between what is happening and what is perceived. C1) So, mind-independent objects are not being per- ceived immediately. C2) So, they are not the immediate objects of per- ception. P2) Direct realism claims that mind-independent ob- jects are the immediate objects of perception. C3) So, direct realism is false.

Argument against time lag

The direct realist can respond in two main ways:

They can argue that the reason for the time delay is due to the nature of the physical medium (photons, air) and so we are still perceiving mind-independent (physical) properties directly.

They can also argue that what we directly perceive is, in fact, the way objects were in the past, due to the physical mechanisms involved. This may sound strange but is a conclusion based on our modern scientific understanding of the world.

Sense data

P1) When we perceive something with property F there is something that F is. P2) In an illusion or hallucination (I+H), the object does not have the property F. C1) So, what has the property F must be something mental, a "sense-datum". C2) So, in I+H sense-data are the immediate objects of perception. P3) I+H are subjectively indistinguishable from veridical perception. C3) So the immediate objects of perception are the same thing interm-12 I+H and in veridical perception. C4) So the immediate objects of perception are always sense-data.

Argument that sense data doesn't exists

Direct realists would argue that illusions can be explained by the concept of relational properties and that hallucinations are not legitimate examples of perception (disjunctivism).

Idealists would argue that the conclusion does not prove sense-data exist, only that the immediate objects of perception are mind-dependent.

existence

P1) Indirect realism claims that physical objects are never the immediate objects of perception. C1) So perceptual experiences can never give us direct evidence that such objects exist. P2) The existence of things can only be proved by experience. C2) So indirect realists cannot prove that physical objects exist.

Proof of existence

P1) Either our sense-data is caused by a mind- independent world, or it is not. P2) If our sense-data are caused by the mind, rather than something mind-independent, then they would be under our voluntary control. P3) But sense-data are not under our control. P4) Our experience of sense-data is coherent. P5) Mind-dependent experiences (e.g. dreams) are often incoherent. C1) The best explanation of our experience is that sense-data are caused by mind-independent objects. C2) So we are justified in believing in mind- independent objects.