Definition of Knowledge

Definition of Knowledge

Basic Concepts

  • Epistemology is the study of knowledge and how it is acquired. It focuses on understanding what constitutes knowledge, how it is obtained, and how it is validated.
  • In philosophy, knowledge is often defined as justified true belief. This is known as the JTB theory.

Justified True Belief (JTB) Theory

  • An individual knows something if and only if they believe it, it is true and they are justified in believing it.


  • A belief is a mental state of acceptance that a statement or proposition is true.
  • Belief alone is not sufficient for knowledge – a belief might be true, but if the person has no justification for holding that belief, then it does not constitute knowledge.


  • Truth is a condition of knowledge. A belief is true if what it claims corresponds to reality.
  • Verifiable truth is an important element in the definition of knowledge.


  • Justification involves the methods or lines of reasoning that support the belief.
  • The belief needs to be justified to distinguish knowledge from lucky guesses or false beliefs that happen to be true.
  • Justification can be inductive, deductive, or based on reliable testimony from others.

Problems with the JTB Theory

  • The Gettier problem challenges the JTB theory, proposing situations where a belief is justified and true, but should not count as knowledge. This is due to the belief’s truth relying on luck rather than genuine justification.

The Concept of Skepticism

  • Skepticism is the philosophical stance which questions the possibility of acquiring knowledge.
  • Skeptics argue that because our perceptions and reason are fallible, any belief derived from them cannot be fully certain hence possibly not constituting knowledge.

Concept of Certainty

  • Some philosophers argue that knowledge requires certainty. Impossibility of doubt or error points towards knowledge.
  • Certainty is different from infallibility. Being incapable of being wrong relates more to the certainty of the belief than the infallibility of the knower.