 Equally important is the relationship between knowledge and obligations, as it is shown by the aforementioned  paradox of epistemic obligation,  which arises within the fusion  (section 3.1)  of a  standard deontic logic  and a standard epistemic logic. But the relationship between these concepts goes beyond their interaction in such a basic system. For example, if an agent does not know about the existence of an obligation, should she be expected to fulfill it? In some cases the answer seems to be “no”: a physician whose neighbor is having a heart attack has no obligation to provide assistance unless she knows about the emergency. Still, in some other cases, the answer seems to be “yes”: the juridical principle “ignorantia juris non excusat” (roughly, ignorance of the law is not excuse) is an example of this.