The incorrigibility of certainty

• There are various kinds of certainty. A belief is psychologically certain when the subject who has it is supremely convinced of its truth.
•  Certainty in this sense is similar to incorrigibility, which is the property a belief has of being such that the subject is incapable of giving it up. 
• But psychological certainty is not the same thing as incorrigibility. 

• A belief can be certain in this sense without being incorrigible; this may happen, for example, when the subject receives a very compelling bit of counterevidence to the (previously) certain belief and gives it up for that reason. 
• Moreover, a belief can be incorrigible without being psychologically certain. For example, a mother may be incapable of giving up the belief that her son did not commit a gruesome murder, and yet, compatible with that inextinguishable belief, she may be tortured by doubt.

A second kind of certainty is epistemic. Roughly characterized, a belief is certain in this sense when it has the highest possible epistemic status. Epistemic certainty is often accompanied by psychological certainty, but it need not be. It is possible that a subject may have a belief that enjoys the highest possible epistemic status and yet be unaware that it does.

Moral certainty is certainty which is sufficient to regulate our behaviour

Certainty is often explicated in terms of indubitability

. For example, a mother may be incapable of giving up the belief that her son did not commit a gruesome murder, and yet, compatible with that inextinguishable belief, she may be tortured by doubt.