Knowledge is the awareness and understanding of facts, truths or information gained in the form of experience or learning. Knowledge is an appreciation of the possession of interconnected details which, in isolation, are of lesser value.
Knowledge is a term with many meanings depending on context, but is (as a rule) closely related to such concepts as meaning, information, instruction, communication, representation, learning and mental stimulus.
Knowledge is distinct from simple information. Both knowledge and information consist of true statements, but knowledge is information that has a purpose or use. Philosophers would describe this as information associated with intentionality. The study of knowledge is called epistemology.
A common definition of knowledge is that it consists of justified true belief. This definition derives from Plato’s Theaetetus. It is considered to set out necessary, but not sufficient, conditions for some statement to count as knowledge.
What constitutes knowledge, certainty and truth are controversial issues. These issues are debated by philosophers, social scientists, and historians. Ludwig Wittgenstein wrote “On Certainty” – aphorisms on these concepts – exploring relationships between knowledge and certainty. A thread of his concern has become an entire field, the philosophy of action.
One way of deriving and verifying knowledge is from tradition or from generally recognized authority. Knowledge may also be claimed for the pronouncements of secular or religious authority such as the state or the church.
In Jewish, Christian and Islamic traditions, there has always been a considerable tension on the issue of authority versus experience in the formation of knowledge. Early Christian philosophy contrasted revelation from God with knowledge gained by reason. St. Augustine for instance put the knowledge of classical philosophers, especially Plato, into a Christian framework. Experimental knowledge was discounted. Early Muslim philosophy, especially the Mutazilite school, medieval Jewish philosophy, and later Christian work, especially that of Thomas Aquinas, focused on Aristotle’s views. These were vast controversies stretching over centuries. The (eventually dominant) Asharite school of Islamic scholars, for instance, strongly rejected most views of Aristotle, while the Roman Catholic tradition generally embraced them. Such efforts to provide an ethical or spiritual basis for the foundations of knowledge continue to this day in the sociology of knowledge, Islamization of knowledge, and the many and varied strains of economics.
A second way to derive knowledge is by observation and experiment. It is not free of uncertainty, as errors of observation or interpretation may occur, and any sense can be deceived by illusions.
Knowledge may also be derived by reason from either traditional, authoritative, or experiential sources or a combination of them. Inferential knowledge is based on reasoning from facts or from other inferential knowledge such as a theory.
Distinguishing knowing that from knowing how
Suppose that Fred says to you: “The fastest swimming stroke is the front crawl. One performs the front crawl by oscillating the legs at the hip, and moving the arms in an approximately circular motion”. Here, Fred has propositional knowledge of swimming and how to perform the front crawl.
However, if Fred acquired this propositional knowledge from an encyclopedia, he will not have acquired the skill of swimming: he has some propositional knowledge, but does not have any procedural knowledge or “know-how“. In general, one can demonstrate know-how by performing the task in question, but it is harder to demonstrate propositional knowledge.
Inferential vs. factual knowledge
Knowledge may be factual or inferential. Factual knowledge is based on direct observation. It is still not free of uncertainty, as errors of observation or interpretation may occur, and any sense can be deceived by illusions.
Inferential knowledge is based on reasoning from facts or from other inferential knowledge such as a theory. Such knowledge may or may not be verifiable by observation or testing. For example, all knowledge of the atom is inferential knowledge. The distinction between factual knowledge and inferential knowledge has been explored by the discipline of general semantics.
Knowledge in philosophy and the problem of justification
For most of philosophical history, “knowledge” was taken to mean a belief that was justified as true to an absolute certainty. Any less justified beliefs were called mere “probable opinion.” Philosophers often define knowledge as a justified, true belief; the branch of philosophy that deals with the nature, origin and scope of knowledge is called epistemology.
But how do we justify that our beliefs are true knowledge? Justification and evidence are both epistemic features of belief. They are, in other words, both qualities that indicate that the belief is true. We could try out other epistemic features in the definition of knowledge, if we wanted to. Instead of “justified true belief” or “true belief with evidence,” we could say that knowledge is “rational true belief” or “warranted true belief.” For our purposes, the differences between these different options don’t matter. The whole point is that, to be knowledge, a belief has to have some positive epistemic feature; it can’t be arbitrary or random or irrational. The Theory of justification deals with these issues in more detail.
A problem with defining knowledge is known as the “Gettier problem”. The Gettier problem arises when we give certain kinds of counterexamples to the JTB (justified true belief) definition. A counterexample is a case where the definition applies, but the word defined doesn’t; or a case where the word defined applies, but the definition doesn’t. Gettier counterexamples are examples where the definition, justified, true belief applies; but one nevertheless still doesn’t have knowledge, so the word “knowledge” doesn’t apply in that case.
Externalist responses to the Gettier problem
Gettier’s article was published in 1963. Right after that, for a good decade or more, there was an enormous number of articles trying to supply the missing fourth condition of knowledge. The big project was to try to figure out the “X” in the equation, Knowledge = belief + truth + justification + X. Whenever someone proposed an answer, someone else would come up with a new counterexample to shoot down that definition.
Some of the proposed solutions involve factors external to the agent. These responses are therefore called externalism. For example, one externalist response to the Gettier problem is to say that the justified, true belief must be caused (in the right sort of way) by the relevant facts.
When scientists or philosophers ask “Is knowledge possible?”, they mean to say “Am I ever sufficiently justified in believing something in order to have knowledge?” Adherents of Philosophical skepticism often say “no”. Philosopical skepticism is the position which critically examines whether the knowledge and perceptions people have is true; adherents of this position hold that one can never obtain true knowledge, since justification is never certain. This is a different position from Scientific skepticism, which is the practical stance that one should not accept the veracity of claims until solid evidence is produced.