To specify, verify, and reason about information security and information assurance, we need a right fundamental logic system to provide us with a logical validity criterion of normative reasoning as well as a formal representation and specification language. The fundamental logic must be able to underlie truth preserving and relevant reasoning in the sense of conditional, ampliative reasoning, paracomplete reasoning, paraconsistent reasoning, and normative reasoning. This paper discusses why classical mathematical logic, its various classical conservatives extensions, or its non-classical alternatives are not suitable candidates for the fundamental logic, shows that deontic relevant logic is a hopeful candidate for the fundamental logic we need.