In philosophy, it is studied above all knowledge in the sense of the state of the one who knows something. The known things themselves are also knowledge, but this second notion is not that which interests the philosophers. Likewise, knowledge, by extension, is also the things that are held for knowledge by an individual or a given society; but here again, philosophers are not interested in this notion, except in debates concerning certain forms of relativism.
Philosophers traditionally distinguish three types of knowledge:
- propositional knowledge is knowing that a certain proposition is true, for example, knowing that the Earth is round;
- objectual knowledge, also called acquaintance, is the fact of knowing a particular thing, for instance, knowing London;
- the know-how is the fact of being able to succeed an action, for example, knowing how to make pancakes.
The definition of propositional knowledge is the one that has attracted the most attention of philosophers. They generally agree that knowledge is a belief that is true, but also that it is not just a true belief. Belief and truth (or fact) must in some way be connected in an appropriate way, but philosophers disagree about the nature of this connection. For some, the belief must be certain or infallible; for others, it must be justified or provided with undefeated justification; for others, it must be the result of a reliable process, or for others that it is not true by accident. It is on these additional conditions for the knowledge that the debates carry.
Tacit and explicit knowledge
Tacit knowledge is often related to personal experience; they combine innate or acquired skills, know-how and experience (they are also called “implicit knowledge”), are generally difficult to verbalize or “formalize”, as opposed to explicit knowledge
Explicit knowledge, as opposed to tacit knowledge, is clearly articulated knowledge on a written document or computer system; this knowledge is physically transferable because it appears in a tangible form such as a paper file or an electronic file.
This distinction is particularly developed by Michael Polanyi.