Knowledge from perception

• Direct Realism


  The immediate objects of perception are mind-independent objects and their properties.
• Indirect Realism


  The immediate objects of perception are mind-dependent objects (sense-data) that are caused by and represent mind-independent objects.
• Idealism


  The external world is mind-dependent.
• Direct realism is often thought of as the common sense theory of perception.
• Differences in perceptual variation provide a problem for direct realism.
• The argument from illusion provides a problem for direct realism.
• The time lag argument provides a problem for direct realism.
• Indirect realism says the immediate object of perception is sense data.
• Sense data


  The content of perceptual experience. It's not a physical thing, it exists in the mind. However, sense data is said to be caused by and represent mind-independent physical objects.
• Primary qualities


  Properties inherent in the object itself. Objective.
• Secondary qualities


  Powers of an object to cause sensations in humans. Subjective.
• Berkeley questions how it's possible for mind-dependent sense data to resemble so-called mind-independent objects.
• Indirect realism leads to scepticism about the nature and existence of the external world.
• Veil of perception


  We can't get beyond the sense data to access the external world behind it.
• Russell argues that the existence of mind-independent objects is the best hypothesis to explain perceptions.
• Locke offers two responses to the sceptical challenge.
• Locke notes how he is unable to avoid having certain sense data produced in his mind when he looks at an object.
• The immediate objects of perception (i.e. ordinary objects such as tables, chairs, etc.) are mind-dependent objects
• Idealism


  The view that there is no external world independent of minds, and we perceive ideas directly. The immediate objects of perception are mind-dependent ideas.
• Unlike direct realism and indirect realism, idealism says there is no mind-independent external world. Instead, idealism claims that all that exists are ideas.
• Idealism says that unless something is being perceived, it doesn't exist
• Bishop George Berkeley: '"Esse est percipi" (to be is to be perceived)'
• Berkeley argues that the very idea of mind-independent objects is inconceivable and impossible
• Berkeley argues that everything we perceive is either a primary quality or a secondary quality, and both are mind-dependent
• Berkeley's master argument is that we cannot even conceive of a mind-independent object because as soon as we conceive of such an object, it becomes mind-dependent
• According to Berkeley, the cause of our perceptions is God, who constantly perceives everything even when we don't
• Idealism makes no distinction between appearance (perception) and reality, which makes it difficult to explain illusions and hallucinations
• Berkeley's response to the argument from illusion is that if something appears crooked, it is crooked, and the 'illusion' is just a mistake about future perceptions
• However, the problem of hallucinations remains, as it is unclear why God would cause such perceptions
• The main argument against direct realism is the problem of hallucinations or illusions, where our perception can be distorted by factors such as sensory input, mental states, or external influences.
• Direct Realism is the view that we perceive objects directly, without any intermediary between us and them.
• Direct realists argue that these experiences are not genuine perceptions but rather misinterpretations of what is actually happening.