No, knowledge does not necessarily require certainty. Fallibilism holds that a person can know something despite a small possibility of error, although infallibilism argues that genuine knowledge must exclude every possibility of being mistaken.
In the traditional justified true belief account, a person knows a proposition when three conditions are met: the proposition is true, the person believes it, and the belief is justified. Certainty is not listed as a separate condition. For example, strong evidence may justify knowing that a train leaves at 09:00 even though an unexpected timetable change remains possible.
Knowledge is factive: if someone knows a proposition, that proposition must be true. However, this does not mean the knower must possess conclusive proof. Fallibilists distinguish truth from the strength of a person's justification: evidence can be sufficient for knowledge without making error logically impossible.
| Position | Does knowledge require certainty? | Main reasoning |
|---|---|---|
| Fallibilism | No | Sufficient, reliable justification can establish knowledge even when error remains possible. |
| Infallibilism | Yes | If a belief could be false, it does not qualify as genuine knowledge. |
| Scepticism | Often yes, producing doubt | Because certainty is difficult or impossible to achieve, little or no knowledge is possible. |
Gettier cases complicate the issue further. They suggest that a belief may be justified and true but still fail to count as knowledge because its truth depends on luck. Increasing a person's subjective confidence does not remove this epistemic luck.
A common misconception is that certainty means feeling completely confident. Psychological certainty is a mental state, while epistemic certainty concerns whether the evidence excludes error. Someone can feel certain and still be wrong.
Exam technique
For a command term such as discuss, define knowledge and certainty, compare fallibilism with infallibilism, and evaluate whether fallible justification is sufficient. Use a clear counterexample and conclude with a defended judgement rather than merely stating that certainty is difficult to achieve.
