When is reasoning with "unknown" knowledge permissible?
E.g. when can one "legitimately" formulate political beliefs or laws based on knowledge, which contains unknowable, unpredictable parts?
If one considers this strictly, then one could claim that "no, it's not possible to accurately infer with unknown knowledge". However, one could also argue that "some things will always contain unknown knowledge, should we therefore still be able to decide on it, even if it's based on subjective bias?".
I personally think that Occam's razor + some others would suggest that inferring with unknown knowledge is not a very good thing. That, while it might "by chance" hit the right spots, it contains too much risk about being very, very erroneous. And that it should be discarded as a methodology because of that.
Also, natural scientific "unknown data" is of different type as e.g. "unknown social data". Natural scientific portion of error can also often be measured or approximately known. Social phenomena on the other hand may well have components which are very, very vaguely understood, even if someone could suggest an explanation.