Knowledge
The owl of Athena, a symbol of knowledge in the Western world, perches on coins minted since ancient times. This image represents a concept that philosophers have debated for millennia. Knowledge is often defined as justified true belief. A person must believe something, it must be true, and they must have good reasons for holding that belief. The third condition, justification, has caused the most trouble for thinkers over the last century. In 1963, epistemologist Edmund Gettier published a paper that challenged this standard definition. He presented thought experiments showing cases where people had beliefs that were both true and justified yet still did not count as knowledge. One famous example involves a man driving down a country road filled with fake barn facades. He stops in front of one real barn by pure luck and forms the belief that he sees a barn. His belief is true because there is a real barn there. It is also justified because his eyes see what looks like a barn. Yet he does not truly know he is looking at a real barn because he could not distinguish it from the fakes. These counterexamples, now called Gettier cases, intensified debates about whether justification alone suffices for knowledge. Philosophers have proposed many alternative definitions to fix these problems. Some argue reliability matters more than justification. Others suggest cognitive virtues play a key role. Still others insist on additional criteria like the absence of false beliefs or defeaters. No single solution has achieved universal consensus in academic discourse.
A person riding a bicycle demonstrates non-propositional knowledge known as knowing-how. This form of practical competence differs sharply from declarative facts stored in books. Propositional knowledge involves relations to propositions expressed through clauses like Akari knows that kangaroos hop. Such knowledge relies on mental representations involving concepts ideas theories and general rules. It often remains context-independent meaning it applies regardless of specific use or purpose. Non-propositional knowledge includes skills like swimming or walking which do not require highly developed minds. An ant knows how to walk even though it lacks the capacity to represent corresponding propositions. Knowledge by acquaintance arises from direct experiential contact with objects people or places. Eating chocolate creates familiarity with its taste while visiting Lake Taupō forms acquaintance with that location. Bertrand Russell first introduced this concept arguing it is more basic than propositional knowledge. To understand any proposition one must be acquainted with its constituents. Mathematical truths such as 2 plus 2 equals 4 traditionally count as a priori knowledge since no empirical investigation confirms them. A posteriori knowledge depends entirely on experience like seeing rain fall outside a window. Some philosophers deny a priori knowledge exists claiming all knowledge requires sensory input. Plato argued souls already possess knowledge needing only recollection to access it again. Descartes proposed innate knowledge present within every human mind. Rational intuition serves as another explanation for non-empirical understanding.
Photos of the five senses illustrate how perception relies on sight sound touch smell and taste to acquire knowledge. Knowing a baby sleeps because you hear snoring counts as observational knowledge derived directly from perception. This active process selects organizes and interprets sensory signals to form environmental representations. Sometimes these processes create illusions like the Müller-Lyer illusion which misrepresents reality. Introspection functions similarly but targets internal mental states rather than external physical objects. Traditionally introspection held special epistemic status considered infallible regarding pain or discomfort. Critics now argue mistakes occur when confusing an itch for pain or mistaking an ellipse for a circle. Memory differs by depending on previous experiences yet remains generally reliable despite occasional degradation. Inferential knowledge emerges when reasoning draws conclusions from known facts like deducing a friend visits Czechia upon seeing a stamp. Rationalists propose rational intuition as a source independent of observation or introspection. Mathematical beliefs such as 2 plus 2 equals 4 may be justified through pure reason alone. Testimony allows one person to learn facts from another without relying on specific cognitive faculties. Regular speech letters newspapers blogs all serve as vehicles for testimony. The reliability of the speaker determines whether testimony leads to genuine knowledge. Only statements from trustworthy sources qualify as valid knowledge under common responses.
A bust of Pyrrho of Elis represents one of history's earliest philosophical skeptics who questioned human capacity for certainty. Radical skepticism holds humans lack any form of knowledge claiming it is impossible altogether. The dream argument suggests perceptual experience provides unreliable information since dreaming mimics waking life. Underdetermination arises when evidence fails to justify choosing between competing theories leading some toward global doubt. Fallibilists accept error possibilities never fully exclude them even within best-researched scientific theories. Pragmatists argue inquiry should aim for well-supported beliefs open to revision rather than absolute truth. Immanuel Kant restricted metaphysical knowledge to appearances excluding things-in-themselves existing independently beyond perception. He concluded no metaphysical knowledge possible regarding world beginnings or infinity. The uncertainty principle states exact magnitudes of certain physical properties like position and momentum cannot known simultaneously. Chaos theory reveals systems so sensitive to initial conditions that predictions become practically impossible. This phenomenon known as the butterfly effect demonstrates how slight variations produce completely different behaviors. Religious skepticism rejects belief in God or doctrines as knowledge lacking sufficient evidence. Moral skepticism claims moral knowledge impossible meaning rightness or wrongness unknowable. Some ideas will never occur to anyone making them inherently unknowable regardless of effort.
A diagram showing differences between foundationalism coherentism and infinitism illustrates three traditional theories of knowledge structure. Foundationalists claim basic reasons possess epistemic status independent of other reasons constituting regress endpoints. Perception self-evident truths like one's own existence serve as examples of such foundational beliefs. Critics question why some reasons qualify as basic while others do not arguing all understanding requires interpretation. Coherentists deny contrasts between basic and non-basic reasons claiming finite mutually supporting justifying beliefs form webs. Mutual support alone fails as good reason for newly accepting both beliefs at once creating circular reasoning risks. Distinct sets of coherent beliefs exist raising questions about which set deserves acceptance. Infinitists embrace infinite chains where each reason depends on another despite human mind limitations. Human minds may lack capacity to hold infinite reasons challenging possibility of knowledge under this view. When challenged a person justifies beliefs by citing sources whose reliability itself demands justification. This process threatens infinite regress since epistemic status at each step depends on previous steps. Three main responses address how mental states relate to form valid knowledge structures without collapsing into contradiction or impossibility.
A sculpture titled Los portadores de la antorcha symbolizes transmission of knowledge from generation to generation in Madrid. Knowledge possesses instrumental value helping achieve goals like passing exams earning money betting correctly. Some beliefs about trivial matters have no practical benefit knowing grain counts on beaches memorizing unused phone numbers. Certain true beliefs hinder action when life depends jumping ravines despite dangers involved. Duncan Pritchard argues forms linked to wisdom possess intrinsic value existing independently of practical benefits. Controversy surrounds whether all knowledge including trivial facts holds inherent worth beyond neutral belief states. Plato's Meno dialogue explores why knowledge better than mere true belief guiding actions equally effectively toward Larissa. Knowledge gains additional stability making it preferable despite equal functional outcomes. Justification adds probability truth but unclear what extra value provided compared unjustified true beliefs. Linda Zagzebski analogized coffee machines producing identical cups regardless reliability failing explain added value reliably formed beliefs. Virtue epistemologists see knowledge as manifestation cognitive virtues inherently valuable independent instrumental usefulness. Acquiring knowledge incurs costs requiring material resources time energy needed understanding decisions. Political leaders allocate funds identifying promising research programs businesses weigh economic benefits against acquisition costs militaries rely intelligence prevent threats educators choose which knowledge pass students.
A replica of the printing press created by Johannes Gutenberg stands as testament to 15th-century technological revolution. Before ancient periods social conduct survival skills passed orally customs from generation next. Major civilizations rose around 3000 BCE in Mesopotamia Egypt India China marking invention writing era. Writing significantly increased stable knowledge stored shared without limited imperfect human memory. Ancient Greeks formalized expanded scientific fields mathematics astronomy medicine starting 6th century BCE. Medieval religious institutions like Catholic Church influenced intellectual activity Jewish yeshivas studied texts laws Muslim madrasa schools focused Islamic philosophy. Islamic Golden Age preserved refined expanded achievements 8th to 13th centuries establishing centers Al-Qarawiyyin University Morocco Al-Azhar Egypt House Wisdom Iraq European universities. Renaissance renewed interest humanities sciences beginning 14th century printing press availability literacy explosion followed. Scientific Revolution Age Enlightenment started 16th 17th centuries exploding physics chemistry biology social sciences. Industrial Revolution 18th 19th centuries accompanied technological advancements enabling mass production. Computers Internet developed 20th century revolutionizing storage sharing creation vast knowledge expansion. History investigates how knowledge created employed disseminated preserved across diverse fields including philosophy mathematics education literature art religion crafts medicine everyday practices.
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Common questions
What is the standard definition of knowledge in philosophy?
Knowledge is often defined as justified true belief. A person must believe something, it must be true, and they must have good reasons for holding that belief.
When did Edmund Gettier publish his paper challenging the definition of knowledge?
In 1963, epistemologist Edmund Gettier published a paper that challenged this standard definition. He presented thought experiments showing cases where people had beliefs that were both true and justified yet still did not count as knowledge.
Who introduced the concept of knowledge by acquaintance?
Bertrand Russell first introduced this concept arguing it is more basic than propositional knowledge. To understand any proposition one must be acquainted with its constituents.
Which philosopher argued souls already possess knowledge needing only recollection to access it again?
Plato argued souls already possess knowledge needing only recollection to access it again. Descartes proposed innate knowledge present within every human mind.
What does radical skepticism claim about human capacity for certainty?
Radical skepticism holds humans lack any form of knowledge claiming it is impossible altogether. The dream argument suggests perceptual experience provides unreliable information since dreaming mimics waking life.
When did major civilizations rise around the invention of writing?
Major civilizations rose around 3000 BCE in Mesopotamia Egypt India China marking invention writing era. Writing significantly increased stable knowledge stored shared without limited imperfect human memory.