
, fact
s, description
s, or skills acquired through experience
or education
. It can refer to the theoretical or practical understanding of a subject. It can be implicit (as with practical skill or expertise) or explicit (as with the theoretical understanding of a subject); and it can be more or less formal or systematic. In philosophy
, the study of knowledge is called epistemology, and the philosopher Plato
famously defined knowledge as "justified true belief
." There is however no single agreed upon definition of knowledge, and there are numerous theories to explain it.
Knowledge acquisition involves complex cognitive
processes: perception, learning, communication, association and reasoning; while knowledge is also said to be related to the capacity of acknowledgment in human beings.
The definition of knowledge is a matter of on-going debate
among philosophers in the field of epistemology.
Knowledge is discovered, when ignorance is lost.
Knowledge is good.
Knowledge is power.
I have taken all knowledge to be my province.
Through wisdom is an house builded; and by understanding it is established: And by knowledge shall the chambers be filled with all precious and pleasant riches.
A man who knows how little he knows is well, a man who knows how much he knows is sick.
The Master said, "Yu, shall I teach you what knowledge is? When you know a thing, to hold that you know it; and when you do not know a thing, to allow that you do not know it; — this is knowledge."
I owe all my knowledge to the German inventor, Johannes Gutenberg!

, fact
s, description
s, or skills acquired through experience
or education
. It can refer to the theoretical or practical understanding of a subject. It can be implicit (as with practical skill or expertise) or explicit (as with the theoretical understanding of a subject); and it can be more or less formal or systematic. In philosophy
, the study of knowledge is called epistemology, and the philosopher Plato
famously defined knowledge as "justified true belief
." There is however no single agreed upon definition of knowledge, and there are numerous theories to explain it.
Knowledge acquisition involves complex cognitive
processes: perception, learning, communication, association and reasoning; while knowledge is also said to be related to the capacity of acknowledgment in human beings.
Theories of knowledge

The definition of knowledge is a matter of on-going debate
among philosophers in the field of epistemology. The classical definition, described but not ultimately endorsed by Plato
, specifies that a statement
must meet three criteria in order to be considered knowledge: it must be justified
, true
, and believed
. Some claim that these conditions are not sufficient, as Gettier case examples allegedly demonstrate. There are a number of alternatives proposed, including Robert Nozick
's arguments for a requirement that knowledge 'tracks the truth' and Simon Blackburn's
additional requirement that we do not want to say that those who meet any of these conditions 'through a defect, flaw, or failure' have knowledge. Richard Kirkham
suggests that our definition of knowledge requires that the evidence for the belief necessitates its truth.
In contrast to this approach, Wittgenstein
observed, following Moore's paradox
, that one can say "He believes it, but it isn't so", but not "He knows it, but it isn't so". He goes on to argue that these do not correspond to distinct mental states, but rather to distinct ways of talking about conviction. What is different here is not the mental state of the speaker, but the activity in which they are engaged. For example, on this account, to know that the kettle is boiling is not to be in a particular state of mind, but to perform a particular task with the statement that the kettle is boiling. Wittgenstein sought to bypass the difficulty of definition by looking to the way "knowledge" is used in natural languages. He saw knowledge as a case of a family resemblance
. Following this idea, "knowledge" has been reconstructed as a cluster concept that points out relevant features but that is not adequately captured by any definition.
Communicating knowledge
Symbolic representations can be used to indicate meaning and can be thought of as a dynamic process. Hence the transfer of the symbolic representation can be viewed as one ascription process whereby knowledge can be transferred. Other forms of communication include observation and imitation, verbal exchange, and audio and video recordings. Philosophers of language and semioticians construct and analyze theories of knowledge transfer or communication.
While many would agree that one of the most universal and significant tools for the transfer of knowledge is writing (of many kinds), argument over the usefulness of the written word exists however, with some scholars skeptical of its impact on societies. In his collection of essays Technopoly
Neil Postman demonstrates the argument against the use of writing through an excerpt from Plato's work Phaedrus (Postman, Neil (1992) Technopoly, Vintage, New York, pp 73). In this excerpt the scholar Socrates
recounts the story of Thamus, the Egyptian king and Theuth the inventor of the written word. In this story, Theuth presents his new invention "writing" to King Thamus, telling Thamus that his new invention "will improve both the wisdom and memory of the Egyptians" (Postman, Neil (1992) Technopoly, Vintage, New York, pp 74). King Thamus is skeptical of this new invention and rejects it as a tool of recollection rather than retained knowledge. He argues that the written word will infect the Egyptian people with fake knowledge as they will be able to attain facts and stories from an external source and will no longer be forced to mentally retain large quantities of knowledge themselves (Postman, Neil (1992) Technopoly, Vintage, New York,pp 74).
Andrew Robinson also highlights, in his work The Origins of Writing, the possibility for writing to be used to spread false information and therefore the ability of the written word to decrease social knowledge (Robinson, Andrew (2003) The Origins of Writing in Crowley and Heyer (eds) Communication in History: Technology, Culture, Society, Boston pp 34). People are often internalizing new information which they perceive to be knowledge but in reality fill their minds with false knowledge.
The above points are moot in the modern world. Verbal communication lends itself to the spread of falsehoods much more so than written, as there is no record of exactly what was said or who originally said it (usually neither the source nor the content can be verified). Gossip and rumors are common examples. As to value of writing, the extent of human knowledge is now so great that it is only possible to record it and to communicate it through writing. Major libraries today can have millions of books of knowledge (in addition to works of fiction). It is only recently that audio and video technology for recording knowledge have become available and the use of these still requires replay equipment and electricity. Verbal teaching and handing down of knowledge is limited to those few who would have contact with the transmitter person - far too limited for today's world. Writing is still the most available and most universal of all forms of recording and transmitting knowledge. It stands unchallenged as mankind's primary technology of knowledge transfer down through the ages and to all cultures and languages of the world.jkj
Situated knowledge
Situated knowledge is knowledge specific to a particular situation.Some methods of generating knowledge, such as trial and error
, or learning from experience
, tend to create highly situational knowledge. One of the main attributes of the scientific method
is that the theories it generates are much less situational than knowledge gained by other methods.
Situational knowledge is often embedded in language, culture, or traditions.
Knowledge generated through experience is called knowledge "a posteriori", meaning afterwards. The pure existence of a term like "a posteriori" means this also has a counterpart. In this case that is knowledge "a priori", meaning before. The knowledge prior to any experience means that there are certain "assumptions" that one takes for granted. For example if you are being told about a chair
it is clear to you that the chair is in space
, that it is 3D. This knowledge is not knowledge that one can "forget", even someone suffering from amnesia experiences the world in 3D. See also: a priori and a posteriori
.
Partial knowledge
One discipline of epistemology focuses on partial knowledge. In most realistic cases, it is not possible to have an exhaustive understanding of an information domain, so then we have to live with the fact that our knowledge is always not complete, that is, partial. Most real problems have to be solved by taking advantage of a partial understanding of the problem context and problem data. That is very different from the typical simple maths problems one might solve at school, where all data is given and one has a perfect understanding of formulas necessary to solve them.This idea is also present in the concept of bounded rationality
which assumes that in real life situations people often have a limited amount of information and make decisions accordingly.
Scientific knowledge
The development of the scientific methodhas made a significant contribution to our understanding of knowledge. To be termed scientific, a method of inquiry
must be based on gathering observable
, empirical
and measurable
evidence
subject to specific principles of reasoning. The scientific method consists of the collection of data
through observation
and experiment
ation, and the formulation and testing of hypotheses. Science, and the nature of scientific knowledge have also become the subject of Philosophy
. As science itself has developed, knowledge has developed a broader usage which has been developing within biology/psychology—discussed elsewhere as meta-epistemology
, or genetic epistemology
, and to some extent related to "theory of cognitive development
".

Until recent times, at least in the Western tradition, it was simply taken for granted that knowledge was something possessed only by humans — and probably adult humans at that. Sometimes the notion might stretch to (ii) Society-as-such, as in (e.g.) "the knowledge possessed by the Coptic culture" (as opposed to its individual members), but that was not assured either. Nor was it usual to consider unconscious knowledge in any systematic way until this approach was popularized by Freud
.
Other biological domains where "knowledge" might be said to reside, include: (iii) the immune system, and (iv) in the DNA of the genetic code. See the list of four "epistemological domains": Popper
, (1975); and Traill (2008: Table S, page 31)—also references by both to Niels Jerne
.
Such considerations seem to call for a separate definition of "knowledge" to cover the biological systems. For biologists, knowledge must be usefully available to the system, though that system need not be conscious. Thus the criteria seem to be:
- The system should apparently be dynamic and self-organizing (unlike a mere book on its own).
- The knowledge must constitute some sort of representation of "the outside world", or ways of dealing with it (directly or indirectly).
- There must be some way for the system to access this information quickly enough for it to be useful.
Scientific knowledge may not involve a claim to certainty
, maintaining skepticism
means that a scientist will never be absolutely certain when they are correct and when they are not. It is thus an irony of proper scientific method
that one must doubt even when correct, in the hopes that this practice will lead to greater convergence on the truth
in general.
Religious meaning of knowledge
In many expressions of Christianity, such as Catholicism
and Anglicanism
, knowledge is one of the seven gifts of the Holy Spirit
.
The Old Testament
's tree of the knowledge of good and evil contained the knowledge that separated Man from God: "And the LORD God said, Behold, the man is become as one of us, to know good and evil…"
In Gnosticism
divine knowledge or gnosis
is hoped to be attained and escape from the demiurge
's physical world. And in Thelema
knowledge and conversation with one's Holy Guardian Angel is the purpose of life, which is similar to Gnosis or enlightenment in other mystery religions.
Hindu
Scriptures present two kinds of knowledge, Paroksha Gnyana and Prataksha Gnyana. Paroksha Gnyana (also spelled Paroksha-Jnana) is secondhand knowledge: knowledge obtained from books, hearsay, etc. Prataksha Gnyana (also spelled Prataksha-Jnana) is the knowledge borne of direct experience, i.e., knowledge that one discovers for oneself. Jyâna yoga ("path of knowledge") is one of three main types of yoga expounded by Krishna
in the Bhagavad Gita
. (It is compared and contrasted with Bhakti Yoga and Karma yoga
.)
In Islam, knowledge (Arabic: علم, ʿilm) is given great significance. "The Knowing" (al-ʿAlīm) is one of the 99 names reflecting distinct attributes of God
. The Qur'an
asserts that knowledge comes from God and various hadith
encourage the acquisition of knowledge. Muhammad
is reported to have said "Seek knowledge from the cradle to the grave" and "Verily the men of knowledge are the inheritors of the prophets". Islamic scholars, theologians and jurists are often given the title alim
, meaning "knowledgable".
In Jewish tradition, knowledge (Hebrew: דעת da'ath) is considered one of the most valuable traits a person can acquire. Observant Jews recite three times a day in the Amidah "Favor us with knowledge, understanding and discretion that come from you. Exalted are you, Existent-One, the gracious giver of knowledge." The Tanakh states, "A wise man gains power, and a man of knowledge maintains power", and "knowledge is chosen above gold".
See also
- Analytic-synthetic distinction
- Descriptive knowledgeDescriptive knowledgeDescriptive knowledge, also declarative knowledge or propositional knowledge, is the species of knowledge that is, by its very nature, expressed in declarative sentences or indicative propositions...
- Epistemic logicEpistemic logicEpistemic modal logic is a subfield of modal logic that is concerned with reasoning about knowledge. While epistemology has a long philosophical tradition dating back to Ancient Greece, epistemic logic is a much more recent development with applications in many fields, including philosophy,...
- Explicit knowledgeExplicit knowledgeExplicit knowledge is knowledge that has been or can be articulated, codified, and stored in certain media. It can be readily transmitted to others. The information contained in encyclopedias are good examples of explicit knowledge....
- Figurative system of human knowledgeFigurative system of human knowledgeThe "figurative system of human knowledge", sometimes known as the tree of Diderot and d'Alembert, was a tree developed to represent the structure of knowledge itself, produced for the Encyclopédie by Jean le Rond d'Alembert and Denis Diderot....
- IntelligenceIntelligenceIntelligence has been defined in different ways, including the abilities for abstract thought, understanding, communication, reasoning, learning, planning, emotional intelligence and problem solving....
- IntuitionIntuition (knowledge)Intuition is the ability to acquire knowledge without inference or the use of reason. "The word 'intuition' comes from the Latin word 'intueri', which is often roughly translated as meaning 'to look inside'’ or 'to contemplate'." Intuition provides us with beliefs that we cannot necessarily justify...
as an unconsciousUnconscious mindThe unconscious mind is a term coined by the 18th century German romantic philosopher Friedrich Schelling and later introduced into English by the poet and essayist Samuel Taylor Coleridge...
form of knowledge. - Knowledge discoveryKnowledge discoveryKnowledge discovery is a concept of the field of computer science that describes the process of automatically searching large volumes of data for patterns that can be considered knowledge about the data . It is often described as deriving knowledge from the input data...
- Knowledge engineeringKnowledge engineeringKnowledge engineering was defined in 1983 by Edward Feigenbaum, and Pamela McCorduck as follows:At present, it refers to the building, maintaining and development of knowledge-based systems...
- Knowledge relativityKnowledge relativityIn philosophy, knowledge relativity is the notion that knowledge can be seen as the relation between a form of representation with up to two sorts of intent – communication and use goals – and with up to three subjects – one who knows, one who is informed, and one who observes and...
- Knowledge retrievalKnowledge retrievalKnowledge Retrieval seeks to return information in a structured form, consistent with human cognitive processes as opposed to simple lists of data items...
- LearningLearningLearning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...
- MetaknowledgeMetaknowledgeMetaknowledge or meta-knowledge is knowledge about a preselected knowledge.For the reason of different definitions of knowledge in the subject matter literature, meta-information is or is not included in meta-knowledge. Detailed cognitive, systemic and epistemic study of human knowledge requires a...
- Philosophical skepticismPhilosophical skepticismPhilosophical skepticism is both a philosophical school of thought and a method that crosses disciplines and cultures. Many skeptics critically examine the meaning systems of their times, and this examination often results in a position of ambiguity or doubt...
- Procedural knowledgeProcedural knowledgeProcedural knowledge, also known as imperative knowledge, is the knowledge exercised in the performance of some task. See below for the specific meaning of this term in cognitive psychology and intellectual property law....
- Society for the Diffusion of Useful KnowledgeSociety for the Diffusion of Useful KnowledgeThe Society for the Diffusion of Useful Knowledge , founded in 1826, and wound up in 1848, was a Whiggish London organisation that published inexpensive texts intended to adapt scientific and similarly high-minded material for the rapidly expanding reading public...
- Tacit knowledgeTacit knowledgeTacit knowledge is knowledge that is difficult to transfer to another person by means of writing it down or verbalising it. For example, stating to someone that London is in the United Kingdom is a piece of explicit knowledge that can be written down, transmitted, and understood by a recipient...
- Berlin Declaration on Open Access to Knowledge in the Sciences and HumanitiesBerlin Declaration on Open Access to Knowledge in the Sciences and HumanitiesThe Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities is a major international statement on open access / access to knowledge. It emerged in 2003 from a conference on open access hosted in Berlin by the Max Planck Society. Organizations that commit to implementing this...
- WisdomWisdomWisdom is a deep understanding and realization of people, things, events or situations, resulting in the ability to apply perceptions, judgements and actions in keeping with this understanding. It often requires control of one's emotional reactions so that universal principles, reason and...