IB Philosophy 3.2 Problems of Knowledge Key Definitions

Arguments from illusion highlight how our senses can present the world as being other than it actually is, as when a straight stick appears bent in water or a white wall looks pink under coloured lighting. These cases are taken to show that what we directly perceive are sense data or mental representations rather than physical objects themselves, motivating indirect realist and idealist theories of perception.

Coherentism is a theory of epistemic justification holding that a belief is justified not by resting on a foundation but by cohering with the wider system of beliefs one already holds, so that mutual support among beliefs replaces the need for self-evident starting points. Critics object that a perfectly coherent set of beliefs could still be entirely divorced from reality, since coherence alone cannot guarantee truth.

Direct realism (also called naive realism) holds that perception gives us unmediated access to the external world as it really is. The objects of perception are the physical things themselves, not mental representations or sense data.

Epistemic justification is the property of a belief that makes it reasonable or rationally held. Within the justified true belief framework, justification distinguishes knowledge from lucky guesses by providing the reasons, evidence, or reliable processes that support a belief's claim to truth.

Foundationalism is a theory of epistemic justification that addresses the regress problem by positing that some beliefs are self-evident or incorrigible, requiring no further justification, and that all other justified beliefs ultimately rest on this secure foundation. The view, associated with Descartes and classical empiricists, faces the challenge of identifying which beliefs genuinely qualify as foundational and whether they can bear the weight placed on them.

Idealism is the metaphysical and epistemological thesis that reality is fundamentally mental or mind-dependent, so that physical objects either reduce to collections of ideas or exist only insofar as they are perceived. Developed by Berkeley and later by Hegel, the view challenges common-sense realism by arguing that we can never step outside experience to verify an independently existing material world.

Epistemological idealism is the view that reality is fundamentally mental or mind-dependent. In its strongest form, associated with Berkeley, physical objects exist only as collections of perceptions, and there is no mind-independent material world.

Nietzsche's perspectivism holds that all knowledge and value judgments arise from a particular perspective, shaped by the interests, drives, and circumstances of the knower, with no neutral 'view from nowhere' from which to evaluate claims absolutely. This does not collapse into relativism, since Nietzsche still distinguishes between life-affirming and life-denying perspectives.

Phenomenalism holds that statements about physical objects are ultimately reducible to statements about actual and possible sensory experiences, so that to say a table exists is just to say that certain visual and tactile sensations would occur under appropriate conditions. The view avoids metaphysical commitments about unobservable matter but struggles to account for unexperienced objects and the regularity of nature.

In the philosophy of the Indian thinker Bhartrhari, pratibha refers to a form of direct, intuitive understanding or flash of insight that grasps meaning holistically, prior to and distinct from propositional analysis. It challenges Western epistemology's focus on propositional knowledge ('knowing that').

Realism in epistemology and metaphysics holds that the external world exists independently of our perception or beliefs about it, and that our senses, when functioning properly, give us at least partially accurate access to this mind-independent reality. The position underpins everyday and scientific reasoning but must answer sceptical challenges about how we can verify the correspondence between our experiences and the world as it actually is.

Reliabilism is an externalist theory of justification holding that a belief is justified if it is produced by a cognitive process that reliably generates true beliefs. The believer need not be aware of the process's reliability for the belief to count as justified.

Scepticism is the philosophical position that knowledge is impossible or severely limited. Sceptics challenge the adequacy of our evidence, the reliability of our cognitive faculties, or the possibility of meeting the conditions required for genuine knowledge.

sensory properties such as colour, sound, taste, smell, and warmth that Descartes and Locke argue do not inhere in external objects but exist only as experiences produced in a perceiving mind. Unlike primary qualities (extension, shape, motion), secondary qualities are mind-dependent responses to the physical micro-structure of matter and tell us less about the objective nature of things than about our own sensory apparatus.

The regress problem challenges the concept of justification by asking what ultimately grounds our beliefs. If every belief must be justified by another, then justification either continues indefinitely (infinite regress), ends in an unjustified belief (foundationalism), or forms a circle (coherentism), each option presenting its own philosophical difficulties.