Theories of knowledge

JTB: Knowledge is justified, true belief.

NFL: According to NFL, knowledge is justified true belief plus there are no false lemmas used to reach that belief.

Infallibilism: JTB+I – the theory of knowledge according to which the justification for your belief must be so strong that your belief is immune to doubt.

Reliabilism: Knowledge is reliably formed, true belief.

VE: Knowledge is virtuously formed, true belief.

A lemma: a premise assumed to be true as a reasoning step towards a true conclusion.

Perception

Direct Realism – Direct realism is a philosophical theory of perception according to which the immediate objects of perception are mind-independent objects and their properties, and we are directly aware of them. In a phrase, we perceive not representations, but the objects themselves.

Indirect Realism – Indirect realism is a philosophical theory of perception according to which the objects of perception are mind-dependent sense data which represent the real, mind-independent objects and their properties. This means we perceive representations, not the objects themselves.

Idealism – An anti-realist theory of perception which claims that there are no mind-independent objects, but there are only mind-dependent ideas which we are directly aware of in perception.

Illusion – An illusion is a non-veridical perceptual experience in which the object of perception is mind-independent, it really does exist in one’s visual field, but the subject perceives it to have a false property. For example, seeing a white vase as if it is red, because a red light has been cast on it.

Hallucination – A hallucination is a non-veridical perceptual experience of an object which does not really exist in one’s visual field, but appears to. This might not be just visual but also hearing sounds of something which is not really there, for example. Hallucinations might be subjectively indistinguishable from veridical experiences.

Perceptual variation – Perceptual variation occurs when the object appears to have different properties from one moment to the next even though it has not changed properties at all e.g., Russell’s case of walking around a table, the table appears to darker or lighter, more oblong or square depending on where he stands, but in reality the shape and colour of the table remains constant throughout.

Reason as a Source of Knowledge

Rationalism as defended by e.g. Descartes, Leibniz, to some extent Kant, claims that reason is the true source of knowledge and so we can, and do, gain substantial knowledge of the world a priori.
[Often, but not always, believe in innate knowledge].

Empiricism: As defended by e.g. Hume, Locke, Berkeley, this is the theory that experience is the true source of knowledge, and so substantial knowledge of the world must be a posteriori.

[Even the analytic truths we know are based on concepts we learnt from experience.
Often, they also deny that we can have innate knowledge].

Innate knowledge – knowledge not derived from/justified by empirical experiences but somehow part of the structure of the mind from birth.

An enthymeme – (from Ancient Greek) is a deductive argument which leaves out a premise, but it still appeals to one’s rationally – we can often look at it and ‘see’ what the missing premise is.

Descartes’ intuition and deduction thesis

Intuition – A non-inferred, direct way of acquiring knowledge, by reasoning alone.

Deduction – Making an inference from other claims. A form of logical argument towards a valid conclusion.

Cogito – Descartes’ claim that he exists: “I am, I exist”.

A priori – Knowledge gained without use of the senses (nor testimony based on someone else’s experience!) but can be worked out with our eyes shut, etc.

Clear and distinct ideas –
Clear = ‘open and present to the attending mind.’
Distinct = clear + ‘precise and separated from other ideas.’ (so, nothing unclear!)

[In Descartes’ words, they are ‘principles of natural light’, ‘self-evident propositions’, ‘eternal truths’, or ‘axioms’].

Indubitable – (of a belief) means it is immune to rational doubt/questioning.

Transcendental argument – arguing that feature x is a precondition of an experience y: so, if you have y, you have x.

Scepticism – the theory that we can/should doubt all knowledge claims.

Local vs global

– Local scepticism: concerns some particular and restricted domain of knowledge, but does not raise doubts about knowledge as a whole, e.g. scepticism about religious language.

– Global scepticism: raise doubts about all of our knowledge e.g. in the evil demon scenario.