I know that one can have a greater or lesser amount of surety (i.e. "I'm not really sure"), but don't you either know or not know something? Are there degrees of knowledge? I hear this phrase often from reporters and news correspondents: "We don't really know…" I think that this is a way to avoid saying "We don't know", which sounds more blunt, but is more precise.
Learn English – Is the “really” in “I don’t really know” necessary
expressionsphrases
Best Answer
Frequently, it is simply a matter of preference. However, the following variations could be interpreted slightly differently.
A simple declaration. Unambiguous.
This is often used to deflect a negative self-assessment. It's common to not want to admit that we don't know something, so we occasionally de-emphasize the declaration.
You didn't mention this variation, but this is often used to do the opposite, actually emphasizing the fact that we don't know. This can be used to stress to someone who may not believe you, that you in fact, really don't know something.
These are really just minor nuances, and the phrases are often used interchangeably. If someone wants to express a degree of knowledge, some other phrase is usually used in conjunction with the declaration. For example, "I don't know enough about X to answer that."