In epistemology, transparency is a property of epistemic states defined as follows:

An epistemic state E is weakly transparent to a subject S if and only if

If and only if

In logic and related fields such as mathematics and philosophy, if and only if is a biconditional logical connective between statements....

when S is in state E, S can know that S is in state E;

an epistemic state E is strongly transparent to a subject S if and only if when S is in state E, S can know that S is in state E, AND when S is not in state E, S can know S is not in state E.

Pain is usually considered to be strongly transparent: when someone is in pain, he knows immediately that he is in pain, and if he is not in pain, he will know he is not.

Transparency is important in the study of self-knowledge and meta-knowledge (knowledge that one knows something).