The 5 Branches of Philosophy
Standard Of Evaluation
Certainty is the acceptance of a fact without doubt. It is a level of confidence attributed to particular knowledge. We are certain when we know something is true, and have no doubts. The term "degrees of certainty" is used to describe how close we are to being certain. Certainty, though, is the upper limit. It is the state where no more doubts exist.
When should one be certain? When all knowledge supports the conclusion, and none denies it. If one has a valid reason for doubting something, one should not be certain. If one, for instance, knows there are facts that are unknown, and important in validating the knowledge, one should not be certain. If, however, one believes that all of the relevant information is known, and it all points to the knowledge being true, one should be certain.
Certainty is contextual. It is based on one's current knowledge. It is possible to be certain, and still be wrong. Human beings are not omniscient. They can form conclusions, but there is the possibility of error. Humans need knowledge, though, and need a basis for accepting knowledge as true. They cannot live constantly doubting every piece of knowledge. To survive, they must be able to accept knowledge as true, and act accordingly.
The term certainty is often used to describe knowledge without the possibility of doubt. This is omniscience. It is an improper use of the term. Certainty could have no meaning when applied to an omniscient being, since it wouldn't have the capacity for doubt. It only has meaning when applied to human beings. Its meaning allows the possibility of error, but the contextual lack of doubt.